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Possible Duplicate:
Hyperref warning - Token not allowed in a PDF string

The following code:

\subsection{The classes $\mathcal{L}(\gamma)$}

generates the errors:

Package hyperref Warning: Token not allowed in a PDF string (PDFDocEncoding):
(hyperref)                removing `math shift' on input line 1938.


Package hyperref Warning: Token not allowed in a PDF string (PDFDocEncoding):
(hyperref)                removing `\gamma' on input line 1938.


Package hyperref Warning: Token not allowed in a PDF string (PDFDocEncoding):
(hyperref)                removing `math shift' on input line 1938.

What do I have to do to keep \gamma in the subsection, so that it is also listed in the table of contents?

marked as duplicate by Werner, Jake, Gonzalo Medina, Mico, Thorsten Apr 27 '12 at 5:58

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

261

The PDF bookmarks are a different thing than the table of contents. The bookmarks are not typeset by TeX: they simply are strings of characters, so no math or general formatting instructions are allowed.

The easiest method to avoid the warnings is to use \texorpdfstring:

\subsection{The classes \texorpdfstring{$\mathcal{L}(\gamma)$}{Lg}}

where in the second argument you put the best approximation possible; after all the bookmarks are only a guide for consulting the document.

  • 2
    Ahh, I see, those are PDF bookmarks, thanks! – Chris Apr 26 '12 at 23:14
  • 1
    Thanks for answering this, even though the question was a duplicate: I couldn't tell if maths mode in section titles would work the same as in the other answers to this problem. – David Roberts May 7 '14 at 0:39
  • In which package is texorpdfstring defined? – Eduardo Jun 7 '16 at 13:52
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    @barbarabeeton The best approximation possible is left to the reader to decide. – egreg Sep 23 '16 at 20:09
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    Note that unicode, with the unicode option set for hyperref, allows a closer representation like ℒ(γ) for the pdf table of content. \subsection{The classes \texorpdfstring{$\mathcal{L}(\gamma)$}{ℒ(γ)}} works as expected, at least on my setup. This works even if unicode characters are not accepted in math mode. – Frédéric Grosshans Mar 20 at 17:59

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