Working with the following abridged line in a BibTeX entry:

author = {J. Pe\~{n}a}

For some reason results in a BibTeX compilation to:

J.~P. {n}a

With a period and a space appearing and the tilde diacritic and the letter e vanishing. I can fix this by wrapping the surname in braces, but am mystified as to why this happens in the first place. Is this expected behaviour?

Thanks for any explanation anyone can offer.

1 Answer 1


Use Pe{\~{n}}a or simply Pe{\~n}a instead.

See https://texfaq.org/FAQ-bibaccent

This is BibTeX's restriction, which is explained in BibTeX's manual btxdoc. Maybe one should check the source code of BibTeX for detailed explanation. However, I think this is not very hard to understand --- In BibTeX, one can use

author = "Kurt G{\"o}del"

How about missing braces? It will be more difficult to write the program for lexical analysis, if the braces can be omitted.

  • BibTeX ignores commands for sorting purposes only if they immediately follow an opening brace. If the brace weren't necessary, you couldn't distinguish between ignored and observed commands.
    – Philipp
    Feb 1, 2011 at 15:16
  • @ Leo Liu: thanks for the clarification. The strange thing is that I have used many diacritics thus far in BibTeX and this is the first time I have run into this restriction, potentially because the diacritic is in the first 3 letters of the first author's surname which means that a condensed reference would (similar to Gödel becoming [Göd31]) be [Peñ10]. This is hidden from me as I am using numerical references. Feb 2, 2011 at 3:40
  • Oddly, author = {Pe\~na, J.} works fine too. Sep 21, 2018 at 0:22

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