Is this bibtex error related to babel

babelbibtexnatbib

I have file that has been running for several years, and as recently as last November. But after updating my MiKTeX today I had to make some changes to avoid new clashes between TikZ and babel. Those changes solved those problems. But now I have a clash apparently between natbib and babel, in a bibliography reference that I did not change.

As an MWE, this source file

\documentclass[11pt]{amsart} 
\usepackage{natbib}
\usepackage[polutonikogreek,english]{babel} 
\begin{document}
  \citet{FerrTheos} 
\bibliographystyle{apalike}
\bibliography{stackref}
\end{document}

produces the problem when stackref.bib has just this entry

@INCOLLECTION{FerrTheos,
  author =       {Ferreir{\'o}s},
  title =        {\textgreek{<O je`os <arijmet'izei} The Rise of Pure Mathematics},
  booktitle =    {The shaping of arithmetic},
  publisher =    {Springer-Verlag},
  year =         {2007},
  editor =       {Catherine Goldstein and ‎Norbert Schappacher and ‎Joachim Schwermer},
}

The file Butcher.bbl shows that bibtex has somehow misread just the initials of the second two editors of the volume. It has turned the letters N and J into the unreadable â:

! LaTeX Error: Invalid UTF-8 byte sequence (â.,).

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...

l.7 \newblock In Goldstein, C., Schappacher, â.,
                                                 and Schwermer, â., editors,...

I have tried many things all too tedious to describe. None worked. How can I fix this?

Best Answer

You have invisible Unicode control characters in your bib file including a U+200e just before the N in Norbert, and another before the J in ‎Joachim

 U+200e LEFT-TO-RIGHT MARK     &lrm;
 U+004e LATIN CAPITAL LETTER N     N
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