Undefined control sequence during compiling

Question

When I am compyling my text in Overleaf I see this message and I have tried to fix it but failed. Can anyone explain how to correct it?

You are using the control sequence \h at line 22 and 27 but it is not defined. Define \h or don't use it. — wipet, May 08 '22 at 18:37
You have the text Finite fields and the (E)rd\h at line 22. There is \h here. I don't know what you mean by \h and TeX don't know too. That is the reason why TeX reports error. And that is the reason why I don't tell you how to define \h because I don't know your intend of using \h. — wipet, May 08 '22 at 18:44
@wipet, that is really weird but there is no such text in my file. — RFZ, May 08 '22 at 18:49
Look in your bibliography file. "Line 22" is possibly in a supplementary file that TeX creates as part of its compilation. — Teepeemm, May 08 '22 at 18:50
@Teepeemm, ohh I see the line 22 in my bibliography file. "TITLE = {Erd\H{o}s distance problem in vector spaces over finite fields}," How to fix that? — RFZ, May 08 '22 at 18:52
You have {E}rd\h{o}s but it may be {E}rd\H{o}s or better Erdős. — wipet, May 08 '22 at 18:56

barbara beeton · Answer 1 · 2022-05-08T20:54:37.777

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The lowercase \h was probably caused by the application of "sentence case" to the title of the bib item. Wrapping braces around just the {E} isn't sufficient in this case; wrap the whole name in braces: {Erd\H{o}s} (or enter it directly, as suggested elsewhere.

This change must be made in the .bib file to persist.

As pointed out by @egreg in a comment, in the author field, Erd{\H{o}}s would be a more correct form.

edited May 08 '22 at 20:54

answered May 08 '22 at 20:30

barbara beeton

88,848

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The correct input for BibTeX should be Erd{\H{o}}s when in the author field, but of course {Erd\H{o}s} is good in the title field. – egreg May 08 '22 at 20:39
Good point. (I'm more used to bibliographies that don't modify the casing of author names.) – barbara beeton May 08 '22 at 20:55

Undefined control sequence during compiling

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