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For any academic/research writing, incorporating references into a document is an important task. Fortunately, LaTeX has a variety of features that make dealing with references much simpler, including built-in support for citing references. However, a much more powerful and flexible solution is achieved thanks to an auxiliary tool called BibTeX (which comes bundled as standard with LaTeX). Recently, BibTeX has been succeeded among many users by BibLaTeX, a tool configurable within LaTeX syntax.

BibTeX provides for the storage of all references in a bibliographic information file with the file extension .bib, a kind of flat-file database. (BibLaTeX uses this same file format but with more and different bibliographic entry types and field types than BibTeX.) This database can be referenced in any LaTeX document, and citations made to any record that is contained within the file. This is often more convenient than embedding them at the end of every document written; a centralized bibliography source can be linked to as many documents as desired (write once, read many!). Of course, bibliographies can be split over as many files as one wishes, so there can be a file containing sources concerning topic A (a.bib) and another concerning topic B (b.bib). When writing about topic AB, both of these files can be linked into the document (perhaps in addition to sources ab.bib specific to topic AB).

If you are writing only one or two documents and aren't planning on writing more on the same subject for a long time, you might not want to waste time creating a database of references you are never going to use. In this case you should consider using the basic and simple bibliography support that is embedded within LaTeX.

LaTeX provides an environment called thebibliography that you have to use where you want the bibliography; that usually means at the very end of your document, just before the \end{document} command. Here is a practical example:

OK, so what is going on here? The first thing to notice is the establishment of the environment. thebibliography is a keyword that tells LaTeX to recognize everything between the begin and end tags as data for the bibliography. The mandatory argument, which I supplied after the begin statement, is telling LaTeX how wide the item label will be when printed. Note however, that the number itself is not the parameter, but the number of digits is. Therefore, I am effectively telling LaTeX that I will only need reference labels of one character in length, which ultimately means no more than nine references in total. If you want more than nine, then input any two-digit number, such as '56', which allows up to 99 references.

Next is the actual reference entry itself. This is prefixed with the \bibitem{cite_key} command. The cite_key should be a unique identifier for that particular reference, and is often some sort of mnemonic consisting of any sequence of letters, numbers and punctuation symbols (although not a comma). I often use the surname of the first author, followed by the last two digits of the year (hence lamport94). If that author has produced more than one reference for a given year, then I add letters after, 'a', 'b', etc. But, you should do whatever works for you. Everything after the key is the reference itself. You need to type it as you want it to be presented. I have put the different parts of the reference, such as author, title, etc., on different lines for readability. These linebreaks are ignored by LaTeX. The \textit{} command formats the title properly in italics.

To actually cite a given document is very easy. Go to the point where you want the citation to appear, and use the following: \cite{cite_key}, where the cite_key is that of the bibitem you wish to cite. When LaTeX processes the document, the citation will be cross-referenced with the bibitems and replaced with the appropriate number citation. The advantage here, once again, is that LaTeX looks after the numbering for you. If it were totally manual, then adding or removing a reference would be a real chore, as you would have to re-number all the citations by hand.

If you want to refer to a certain page, figure or theorem in a text book, you can use the arguments to the \cite command:

The argument, "p. 215", will show up inside the same brackets. Note the tilde in [p.~215], which replaces the end-of-sentence spacing with a non-breakable inter-word space. This non-breakable inter-word space is inserted because the end-of-sentence spacing would be too wide, and "p." should not be separated from the page number. The code \cite[215]{citation01} will produce the same result — in this case p.~ in front of the page number will be added automatically; but it will not be added for \cite[Cor.~2.5]{citation01}.

When a sequence of multiple citations is needed, you should use a single \cite{} command. The citations are then separated by commas. Here's an example:

The result will then be shown as citations inside the same brackets, depending on the citation style.

There are several different ways to format lists of bibliographic references and the citations to them in the text. These are called citation styles, and consist of two parts: the format of the abbreviated citation (i.e. the marker that is inserted into the text to identify the entry in the list of references) and the format of the corresponding entry in the list of references, which includes full bibliographic details.

Abbreviated citations can be of two main types: numbered or textual. Numbered citations (also known as the Vancouver referencing system) are numbered consecutively in order of appearance in the text, and consist in Arabic numerals in parentheses (1), square brackets [1], superscript1, or a combination thereof[1]. Textual citations (also known as the Harvard referencing system) use the author surname and (usually) the year as the abbreviated form of the citation, which is normally fully (Smith 2013) or partially enclosed in parenthesis, as in Smith (2013). The latter form allows the citation to be integrated in the sentence it supports.

Below you can see three of the styles available with LaTeX:

Here are some more often used styles:

However, keep in mind that you will need to use the natbib package to use most of these.

If you only want a reference to appear in the bibliography, but not where it is referenced in the main text, then the \nocite{} command can be used, for example:

A special version of the command, \nocite{*}, includes all entries from the database, whether they are referenced in the document or not.

Using the standard LaTeX bibliography support, you will see that each reference is numbered and each citation corresponds to the numbers. The numeric style of citation is quite common in scientific writing. In other disciplines, the author-year style, e.g., (Roberts, 2003), such as Harvard is preferred. The natbib package is one possible way to get such an output. In fact, it can supersede LaTeX's own citation commands, as Natbib allows the user to easily switch between Harvard or numeric.

The first job is to add the following to your preamble in order to get LaTeX to use the Natbib package:

An example of useful options is:

Also, you need to change the bibliography style file to be used, so edit the appropriate line at the bottom of the file so that it reads: \bibliographystyle{plainnat}. Once done, it is basically a matter of altering the existing \cite commands to display the type of citation you want.

The main commands simply add a t for 'textual' or p for 'parenthesized', to the basic \cite command. You will also notice how Natbib by default will compress references with three or more authors to the more concise 1st surname et al version. By adding an asterisk (*), you can override this default and list all authors associated with that citation. There are some other specialized commands that Natbib supports, listed in the table here. Keep in mind that for instance abbrvnat does not support \citet* and will automatically choose between all authors and et al..

The final area that I wish to cover about Natbib is customizing its citation style. There is a command called \bibpunct that can be used to override the defaults and change certain settings. For example, I have put the following in the preamble:

The command requires six mandatory parameters.

Some of the options controlled by \bibpunct are also accessible by passing options to the natbib package when it is loaded. These options also allow some other aspect of the bibliography to be controlled, and can be seen in the table (right).

So as you can see, this package is quite flexible, especially as you can easily switch between different citation styles by changing a single parameter. Do have a look at the Natbib manual, it's a short document and you can learn even more about how to use it.

I have previously introduced the idea of embedding references at the end of the document, and then using the \cite command to cite them within the text. In this tutorial, I want to do a little better than this method, as it's not as flexible as it could be. I will concentrate on using BibTeX.

A BibTeX database is stored as a .bib file. It is a plain text file, and so can be viewed and edited easily. The structure of the file is also quite simple. An example of a BibTeX entry:

Each entry begins with the declaration of the reference type, in the form of @type. BibTeX knows of practically all types you can think of, common ones are: book, article, and for papers presented at conferences, there is inproceedings. In this example, I have referred to an article within a journal.

After the type, you must have a left curly brace '{' to signify the beginning of the reference attributes. The first one follows immediately after the brace, which is the citation key, or the BibTeX key. This key must be unique for all entries in your bibliography. It is this identifier that you will use within your document to cross-reference it to this entry. It is up to you as to how you wish to label each reference, but there is a loose standard in which you use the author's surname, followed by the year of publication. This is the scheme that I use in this tutorial.

Next, it should be clear that what follows are the relevant fields and data for that particular reference. The field names on the left are BibTeX keywords. They are followed by an equals sign (=) where the value for that field is then placed. BibTeX expects you to explicitly label the beginning and end of each value. I personally use quotation marks ("), however, you also have the option of using curly braces ('{', '}'). But as you will soon see, curly braces have other roles, within attributes, so I prefer not to use them for this job as they can get more confusing. A notable exception is when you want to use characters with umlauts (ü, ö, etc), since their notation is in the format \"{o}, and the quotation mark will close the one opening the field, causing an error in the parsing of the reference. Using \usepackage[utf8]{inputenc} in the preamble to the .tex source file can get round this, as the accented characters can just be stored in the .bib file without any need for special markup. This allows a consistent format to be kept throughout the .bib file, avoiding the need to use braces when there are umlauts to consider.

Remember that each attribute must be followed by a comma to delimit one from another. You do not need to add a comma to the last attribute, since the closing brace will tell BibTeX that there are no more attributes for this entry, although you won't get an error if you do.

It can take a while to learn what the reference types are, and what fields each type has available (and which ones are required or optional, etc). So, look at this entry type reference and also this field reference for descriptions of all the fields. It may be worth bookmarking or printing these pages so that they are easily at hand when you need them. Much of the information contained therein is repeated in the following table for your convenience.

+ Required fields, o Optional fields *1 (Clarification needed) *2 (Clarification needed)

BibTeX can be quite clever with names of authors. It can accept names in forename surname or surname, forename. I personally use the former, but remember that the order you input them (or any data within an entry for that matter) is customizable and so you can get BibTeX to manipulate the input and then output it however you like. If you use the forename surname method, then you must be careful with a few special names, where there are compound surnames, for example "John von Neumann". In this form, BibTeX assumes that the last word is the surname, and everything before is the forename, plus any middle names. You must therefore manually tell BibTeX to keep the 'von' and 'Neumann' together. This is achieved easily using curly braces. So the final result would be "John {von Neumann}". This is easily avoided with the surname, forename, since you have a comma to separate the surname from the forename.

Secondly, there is the issue of how to tell BibTeX when a reference has more than one author. This is very simply done by putting the keyword and in between every author. As we can see from another example:

This book has three authors, and each is separated as described. Of course, when BibTeX processes and outputs this, there will only be an 'and' between the penultimate and last authors, but within the .bib file, it needs the ands so that it can keep track of the individual authors.

Standard templates that can be directly copied and filled in. Optional entries are marked in the core by a ? prefix. Note that the % sign used in LaTeX for commenting lines does not work in BibTeX and creates invalid field name. In BibTeX, valid but unknown field names and names outside of an entry are ignored, leading to a popular commenting method. <--Be careful if you copy the following templates, the % sign is not valid to comment out lines in bibtex files. If you want to comment out a line, you have to put it outside the entry.-->

In the event that BibTeX has been set by the chosen style not to preserve all capitalization within titles, problems can occur, especially if you are referring to proper nouns, or acronyms. To tell BibTeX to keep them, use the good old curly braces around the letter in question, (or letters, if it's an acronym) and all will be well! It is even possible that lower-case letters may need to be preserved - for example if a chemical formula is used in a style that sets a title in all caps or small caps, or if "pH" is to be used in a style that capitalises all first letters.

However, avoid putting the whole title in curly braces, as it will look odd if a different capitalization format is used:

For convenience though, many people simply put double curly braces, which may help when writing scientific articles for different magazines, conferences with different BibTex styles that do sometimes keep and sometimes not keep the capital letters:

As an alternative, try other BibTex styles or modify the existing. The approach of putting only relevant text in curly brackets is the most feasible if using a template under the control of a publisher, such as for journal submissions. Using curly braces around single letters is also to be avoided if possible, as it may mess up the kerning, especially with biblatex,[1] so the first step should generally be to enclose single words in braces.

Below you will find a few additional examples of bibliography entries. The first one covers the case of multiple authors in the Surname, Firstname format, and the second one deals with the incollection case.

If you have to cite a website you can use @misc, for example:

The note field comes in handy if you need to add unstructured information, for example that the corresponding issue of the journal has yet to appear:

At the end of your LaTeX file (that is, after the content, but before \end{document}), you need to place the following commands:

Bibliography styles are files recognized by BibTeX that tell it how to format the information stored in the .bib file when processed for output. And so the first command listed above is declaring which style file to use. The style file in this instance is plain.bst (which comes as standard with BibTeX). You do not need to add the .bst extension when using this command, as it is assumed. Despite its name, the plain style does a pretty good job (look at the output of this tutorial to see what I mean).

The second command is the one that actually specifies the .bib file you wish to use. The ones I created for this tutorial were called sample1.bib, sample2.bib, . . ., samplen.bib, but once again, you don't include the file extension. At the moment, the .bib file is in the same directory as the LaTeX document too. However, if your .bib file was elsewhere (which makes sense if you intend to maintain a centralized database of references for all your research), you need to specify the path as well, e.g \bibliography{/some/where/sample} or \bibliography{../sample1} (if the .bib file is in the parent directory of the .tex document that calls it).

Now that LaTeX and BibTeX know where to look for the appropriate files, actually citing the references is fairly trivial. The \cite{ref_key} is the command you need, making sure that the ref_key corresponds exactly to one of the entries in the .bib file. If you wish to cite more than one reference at the same time, do the following: \cite{ref_key1, ref_key2, ..., ref_keyN}.

The addition of BibTeX adds extra complexity for the processing of the source to the desired output. This is largely hidden from the user, but because of all the complexity of the referencing of citations from your source LaTeX file to the database entries in another file, you actually need multiple passes to accomplish the task. This means you have to run LaTeX a number of times. Each pass will perform a particular task until it has managed to resolve all the citation references. Here's what you need to type (into command line):

(Extensions are optional, if you put them note that the bibtex command takes the AUX file as input.)

After the first LaTeX run, you will see errors such as:

The next step is to run bibtex on that same LaTeX source (or more precisely the corresponding AUX file, however not on the actual .bib file) to then define all the references within that document. You should see output like the following:

The third step, which is invoking LaTeX for the second time will see more errors like "LaTeX Warning: Label(s) may have changed. Rerun to get cross-references right.". Don't be alarmed, it's almost complete. As you can guess, all you have to do is follow its instructions, and run LaTeX for the third time, and the document will be output as expected, without further problems.

If you want a pdf output instead of a dvi output you can use pdflatex instead of latex as follows:

(Extensions are optional, if you put them note that the bibtex command takes the AUX file as input.)

Note that if you are editing your source in vim and attempt to use command mode and the current file shortcut (%) to process the document like this:

You will get an error similar to this:

It appears that the file extension is included by default when the current file command (%) is executed. To process your document from within vim, you must explicitly name the file without the file extension for bibtex to work, as is shown below:

Another option exists if you are running Unix/Linux or any other platform where you have make. Then you can simply create a Makefile and use vim's make command or use make in shell. The Makefile would then look like this:

As you can see, there is no field for URLs. One possibility is to include Internet addresses in howpublished field of @misc or note field of @techreport, @article, @book:

howpublished = "\url{http://www.example.com}"

Note the usage of \url command to ensure proper appearance of URLs.

Another way is to use special field url and make bibliography style recognise it.

url = "http://www.example.com"

You need to use \usepackage{url} in the first case or \usepackage{hyperref} in the second case.

Styles provided by Natbib (see below) handle this field, other styles can be modified using urlbst program. Modifications of three standard styles (plain, abbrv and alpha) are provided with urlbst.

If you need more help about URLs in bibliography, visit FAQ of UK List of TeX.

One of the main advantages of BibTeX, especially for people who write many research papers, is the ability to customize your bibliography to suit the requirements of a given publication. You will notice how different publications tend to have their own style of formatting references, to which authors must adhere if they want their manuscripts published. In fact, established journals and conference organizers often will have created their own bibliography style (.bst file) for those users of BibTeX, to do all the hard work for you.

It can achieve this because of the nature of the .bib database, where all the information about your references is stored in a structured format, but nothing about style. This is a common theme in LaTeX in general, where it tries as much as possible to keep content and presentation separate.

A bibliography style file (.bst) will tell LaTeX how to format each attribute, what order to put them in, what punctuation to use in between particular attributes etc. Unfortunately, creating such a style by hand is not a trivial task. Which is why Makebst (also known as custom-bib) is the tool we need.

Makebst can be used to automatically generate a .bst file based on your needs. It is very simple, and actually asks you a series of questions about your preferences. Once complete, it will then output the appropriate style file for you to use.

It should be installed with the LaTeX distribution (otherwise, you can download it) and it's very simple to initiate. At the command line, type:

LaTeX will find the relevant file and the questioning process will begin. You will have to answer quite a few (although, note that the default answers are pretty sensible), which means it would be impractical to go through an example in this tutorial. However, it is fairly straight-forward. And if you require further guidance, then there is a comprehensive manual available. I'd recommend experimenting with it and seeing what the results are when applied to a LaTeX document.

If you are using a custom built .bst file, it is important that LaTeX can find it! So, make sure it's in the same directory as the LaTeX source file, unless you are using one of the standard style files (such as plain or plainnat, that come bundled with LaTeX - these will be automatically found in the directories that they are installed. Also, make sure the name of the .bst file you want to use is reflected in the \bibliographystyle{style} command (but don't include the .bst extension!).

When writing documents in languages other than English, you may find it desirable to adapt the appearance of your bibliography to the document language. This concerns words such as editors, and, or in as well as a proper typographic layout. The babelbib package can be used here. For example, to layout the bibliography in German, add the following to the header:

Alternatively, you can layout each bibliography entry according to the language of the cited document:

The language of an entry is specified as an additional field in the BibTeX entry:

For babelbib to take effect, a bibliography style supported by it - one of babplain, babplai3, babalpha, babunsrt, bababbrv, and bababbr3 - must be used:

Usually LaTeX only displays the entries which are referred to with \cite. It's possible to make uncited entries visible:

Many online databases provide bibliographic data in BibTeX-Format, making it easy to build your own database. For example, Google Scholar offers the option to return properly formatted output, which can also be turned on in the settings page.

One should be alert to the fact that bibliographic databases are frequently the product of several generations of automatic processing, and so the resulting BibTex code is prone to a variety of minor errors, especially in older entries.

Although it can take a little time to get to grips with BibTeX, in the long term, it's an efficient way to handle your references. It's not uncommon to find .bib files on websites that people compile as a list of their own publications, or a survey of relevant works within a given topic, etc. Or in those huge, online bibliography databases, you often find BibTeX versions of publications, so it's a quick cut-and-paste into your own .bib file, and then no more hassle!

Having all your references in one place can be a big advantage. And having them in a structured form, that allows customizable output is another one. There are a variety of free utilities that can load your .bib files, and allow you to view them in a more efficient manner, as well as sort them and check for errors.

If you are writing a book or report, you'll likely insert your bibliography using something like:

Or, if you are using BibTeX, your references will be saved in a .bib file, and your TeX document will include the bibliography by these commands:

Both of these examples will create a chapter-like (or section-like) output showing all your references. But even though the resulting “References” looks like a chapter or section, it will not be handled quite the same: it will not appear in the Table of Contents.

The most comfortable way of adding your bibliography to the table of contents is to use the dedicated package tocbibind that works with many standard document classes. Simply include this code in the preamble of your document:

This will include the Bibliography in the Table of Contents without numbering. If you want to have proper numbering, include the following code in the preamble:

The tocbibind package can also handle including the List of Figures, List of Tables and the Table of Contents itself in the Table of Contents. It has many options for numbering, document structure etc. to fit almost any scenario. See the tocbibind CTAN page for detailed documentation.

If you want your bibliography to be in the table of contents, just add the following two lines just before the thebibliography environment:

(OR \addcontentsline{toc}{section}{Bibliography} if you're writing an article)

The first line just terminates the current paragraph and page. If you are writing a book, use \cleardoublepage to match the style used. The second line will add a line in the Table of Contents (first option, toc), it will be like the ones created by chapters (second option, chapter), and the third argument will be printed on the corresponding line in the Table of Contents; here Bibliography was chosen because it's the same text the thebibliography environment will automatically write when you use it, but you are free to write whatever you like. If you are using a separate bib file, add these lines between \bibliographystyle and \bibliography.

If you use hyperref package, you should also use the \phantomsection command to enable hyperlinking from the table of contents to bibliography.

This trick is particularly useful when you have to insert the bibliography in the Table of Contents, but it can work for anything. When LaTeX finds the code above, it will record the info as described and the current page number, inserting a new line in the Contents page.

If you instead want bibliography to be numbered section or chapter, you'll likely use this way:

Another even easier solution is to use \section inside of the \renewcommand block:

You may wish to use \renewcommand*{\refname}{\vspace*{-1em}} followed by \vspace*{-1em} to counteract the extra space the blank \refname inserts.

If you are using BibTeX, the \bibliography command, and the book or report class, you will need to redefine \bibname instead of \refname like so.

As we said before, biblatex is widely considered the successor of BibTeX. Intended as a full replacement for BibTeX, it is more configurable in its output and provides a multitude of new styles (for output) and fields (for the database) that can be used in a document. For now, refer to its comprehensive documentation on CTAN.

The following table shows most field types. Some field types are lists, either lists of person names, others are literal lists. A date can either be given in parts or full, some keys are necessary, page references are provided as ranges and certain special fields contain verbatim code. There are many kinds of titles.

Some entry types are hard to distinguish and are treated the same by standard styles:

Some field types are defined, but the documentation does not say which entry types they can be used with. This is either because they depend on another field being set to be useful or they can always be used in a user-defined manner, but will never be used in standard styles:

The only field that is always mandatory, is title. All entry types also require either date or year and they specify which of author and editor they expect or whether they can use both. Some field types can optionally be used with any entry type:

All physical (print) entry types share further optional field types:

Multimedia entry types

and legal entry types

are defined, but not yet supported (well).

The entry types @bibnote, @set and @xdata are special.

Presuming we have defined our references in a file called references.bib, we add this to biblatex by adding the following to the preamble:

Print the bibliography with this macro (usually at the end of the document body):

We want to separate the bibliography into papers, books and others

If the bib entries are located in multiple files we can add them like this:

We can also filter on other fields, such as entrysubtype. If we define our online resources like this:

we filter with \printbibliography[title={Online resources}, subtype=inet]

As the numbering of the bibliographies are independent, it can be useful to also separate the bibliographies using prefixnumbers such as a, b and c. In addition we add a main heading for the bibliographies and add that to the table of contents.

To make Hyperref links point to the correct bibliography section, we also add \phantomsection before printing each bibliography

To add each of the bibliographies to the table of contents as sub-sections to the main Bibliography, replace heading=subbibliography with heading=subbibintoc.

This package is for multiple Bibliographies for different sections in your work. For example, you can generate a bibliography for each chapter. You can find information about the package on CTAN[2]

The bibtopic-Package[3] is created to split the citations among more files, so that you can divide the bibliography into more parts. It generates a separate aux file for each bibliography section, so you will have to run bibtex on each of those (see the package documentation for more details).

This page uses material from Andy Roberts' Getting to grips with LaTeX with permission from the author.

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• When the proper selection is made, turn off the unit using the Power button.

San Francisco's fire department uses wooden ladders to reduce the risk of electrocution from overhead lines.Here is a good video about how they make the ladders.

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In the 90s it was the main method of communication between people, even above voice calls, but now it is more associated with banking operations or security confirmations. In 2012 some 15 million SMS were sent every minute and one study said they were the most popular form of communication. The situation changed dramatically as a result of the popularity of the application, which was originally created for theBlackBerry devices and later became available for the Apple iPhone and for phones with theANDROID operating system.

Statista is a source.

The idea of adding text messaging to mobile user services was already present in many mobile communication service communities.

Let us remember that SMS are sent through signaling channels, the use of which was not intended for communication between users, but rather was devised as a way of notifying the user of services such as missed calls or voicemail messages, without However, over time it evolved into a system for sending text messages from one mobile user to another.

Due to its small size, SMS does not require a radio channel to be assigned to the user, which is why it can be received even during a voice call.

In February 1985 the document "Services and Facilities to be provided in the sg system" mentioned the possibility of a service called "sms".

The first commercial text message was sent on December 3, 1992 in the United States and it was Merry Christmas.

Friedhelm Hillebrand, the German engineer who created the text messaging service, thought that 160 characters was enough to send a message.

Hillebrand randomly type in several questions and phrases on his typewriter to see how many characters he used and whether he could convey his ideas and thoughts in that length of text. He came to the conclusion that most of them were less than 160 characters, so they were set as the maximum.

The function that allowed the user to write a message of up to 640 characters, which was cut into 4 parts to be sent, allowed messages to somehow expand their capacity.

A sim card that is used to store information such as contacts and text messages can be found on the back of a mobile phone.

Remember that when GSM mobile telephony arose in Spain (1995) mobile phones barely had internal storage capacity as they do now, and therefore the SIM card, outside of 32k or 64kb, allowed even greater storage capacity for contacts and SMS. than the phone itself, which is why the SIM became a kind of backup. The devices that allowed the customer to save a backup copy of their sim came to be marketed.