82

I see in some examples each field in a BibTeX entry is given within "", while in others it is given within {}. For example,

@Book{Torre2008,
 author    = "Joe Torre and Tom Verducci",
 publisher = "Doubleday",
 title     = "The Yankee Years",
 year      =  2008,
 isbn      = "0385527403"
}

@PROCEEDINGS {conference:06,
 editor    = {First Editor and Second Editor},
 title     = {Proceedings of the Xth Conference on XYZ},
 booktitle = {Proceedings of the Xth Conference on XYZ},
 year      = {2006},
 month     = oct,
}

What are the differences between the two? Which one should I use?

Marco Daniel
  • 95,681

2 Answers2

63

In addition to the points made by @MarcoDaniel in his answer, I'd also mention that

  • Double-quote marks and (paired) curly braces are equally valid as outer delimiters for an entire field, as you show in the two example bib entries.

    • Care has to be taken, though, if double-quote marks can appear inside a field -- see the example posted by Marco D. If there's a chance that double-quotes will appear inside a field, it's necessary to use curly braces for the outer delimiters or to encase the double-quote symbols in curly braces.

  • Sometimes it's necessary to use inner delimiters, i.e., within a field. For such cases it's definitely better to use pairs of curly braces. Examples of such cases are:

    • Dealing with "corporate authors" (any name, really, that can't be decomposed into first name, von, and surname components). For instance, one needs to write 

      author = "{National Aeronautics and Space Administration}",

      or, equivalently,

      author = {{National Aeronautics and Space Administration}},

      to inform BibTeX that this entry has a single "corporate" author rather than two "ordinary" authors.

      Recall that the word "and" has a reserved meaning in BibTeX when used in an author or editor field. Continuing with the NASA example, if you do not indicate to BibTeX that the entry's author is "corporate" rather than personal, it'll merrily (mis-)interpret the and particle and treat the author field as consisting of two authors: the first named "National Aeronautics" (given name: National, surname: Aeronotics), and the second named "Space Administration" (given name: Space, surname: Administration). No kidding! You and your readers will appreciate not having to deal with citations such as "Aeronautics and Administration (1982)" and the entry being rendered as "Aeronautics, N., and Administration, S." and sorted under "A" for "Aeronautics" rather than under "N" for "National".

    • Preventing words in title fields from being converted to lowercase if "sentence style" (as is the case with many bibliography styles) rather than "title style" typesetting is in effect. E.g., you should use curly braces to write 

      title = "The Life of {Albert} {Einstein}",

      or, equivalently, 

      title = {The life of {Albert} {Einstein}},

      to ensure that the letters "A" and "E" will always be typeset in uppercase mode even if "sentence style" is in effect.

Mico
  • 506,678
  • It is better to place in curlies just the needed letters, i.e. {A}lbert instead of {Albert}. I picked this up a while back in some BibTeX site, sorry I forgot details on why, perhaps to not interfere with hyphenating out such. – vonbrand Jun 02 '14 at 03:40
  • @vonbrand - Actually, there seems to be a lot of campfire folklore out there regarding where the curlies should be placed -- just around the needed letters or around the entire word? AFAICT, either method works without side-effects. I personally find it easier to read the entries if the curlies surround the entire word, so that's why I use that approach... – Mico Jun 02 '14 at 04:35
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    The folklore goes the other way too. See http://tex.stackexchange.com/questions/10772/bibtex-loses-capitals-when-creating-bbl-file and the answer by alexis (Including Graphical Example :) ) – Bananach Nov 27 '15 at 14:15
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    @Mico One side effect of using {A}bc is that there is no proper letter spacing (kerning) between A and b. {Abc} does not suffer from this problem. – Nico Schlömer Oct 28 '17 at 10:16
  • @NicoSchlömer - Are you saying any special kerning is performed (or should be performed between A and b? – Mico Oct 28 '17 at 11:00
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    @Mico The use of brackets prevents kerning. Compare AV and {A}V, in any LaTeX document, for example. – Nico Schlömer Oct 28 '17 at 11:15
  • In your last example, the curly example does not have "life" capitalized compared with the quotes example. Is that on purpose? – Bram Vanroy Nov 19 '19 at 10:09
  • @BramVanroy - Short answer: Maybe. Longer answer: I honestly don't remember why I wrote various things back in April 2013, i.e., more than 6 1/2 years ago. For sure, the main purpose of the final part of the answer was to show how one might prevent the lowercasing of the words "Albert" and "Einstein" in the title field of a bibliographic entry. If it bothers you that I wrote "Life" in one instance and "life" in the other, I can edit the answer to establish uniformity in this regard. – Mico Nov 19 '19 at 14:35
  • It doesn't bother me. I was genuinely curious. I am still not sure what the best practice is for bibtext since many bib managers (e.g. Zotero, Mendely) add forceful curly brackets in all places that the original paper used capital letters. However, in many style guides you would use sentence case, meaning you'd have to change all bibtex files generated by these tools to sentence case. – Bram Vanroy Nov 19 '19 at 15:16
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    @BramVanroy - My attitude toward Zotero, Mendeley, and other tools: Be very careful, and very skeptical. Whenever I've used these tools, I find that whereas the majority of the bib entries they produce is factually correct, too many other entries they produce are riddled with errors of content. One simply mustn't assume that the contents of a bib file are correct just because the bib file was created by some software app. – Mico Nov 19 '19 at 16:04
42

Let me reference to the document Tame the BeaST -- The B to X of BibTeX chapter 8 page 20

  • Values (i.e. right hand sides of each assignment) can be either between curly braces or between double quotes. The main difference is that you can write double quotes in the first case, and not in the second case. For citing Comments on “Filenames and Fonts” by Frank Mittelbach, you can use one of the following solutions: 

    title = "Comments on {"}Filenames and Fonts{"}",
title = {Comments on "Filenames and Fonts"},

    Curly braces have to match, since they will appear in the output to be compiled by LaTeX. A problem occurs if you need to write a (left-, say) brace in an entry. You could of course write \{, but the entry will have to also include the corresponding right brace. To include a left brace without its corresponding right brace, you’ll have use a LaTeX function having no brace in its name. \leftbrace is the right choice here. Another solution is to add an extra \bgroup in the entry, so that both LaTeX and BibTeX will find the correct number of “braces

  • For numerical values, curly braces and double quotes can be omitted

Marco Daniel
  • 95,681