# Undefined control sequence error in \cite

 \documentclass{aa}
\begin{document}
Most ordinary chondrites have lower coercivity than their main constituent ferromagnetic phases (\‍‍‍cite{gattacceca2003magnetic}). Different meteorites have significantly different magnetic properties. The coercivity of different meteorite classes is 1.78 mT for H chondrites, 5.62 mT for L chondrites and 36.40 mT  for LL chondrites.  This is true that LL chondrites have higher coercivity than L and H chondrites, because of increasing Fe content of the silicates from H to LL chondrites (\‍‍‍‍cite{gattacceca2003magnetic}).

\‍‍‍‍end{document}


the bibtex:

@article{gattacceca2003magnetic,
title={Magnetic properties of a freshly fallen LL ordinary chondrite: the Bensour meteorite},
author={Gattacceca, J{\'e}r{\^o}me and Rochette, Pierre and Bourot-Denise, Mich{\e}le},
journal={Physics of the Earth and Planetary Interiors},
volume={140},
number={4},
pages={343--358},
year={2003},
publisher={Elsevier}
}


the error:

! Undefined control sequence.
l.296 ...main constituent ferromagnetic phases (\�
��‍‍cite{gattacceca200...

• You have some weird invisible characters (zero-width joiners) in (\‍‍‍cite{gattacceca2003magnetic}) specifically between the backslash and the c of cite. Delete that bit and re-type it. – moewe Feb 11 at 13:54
• @moewe I did. But still the error exists. – Yasamin Feb 11 at 13:55
• Did you do that for all occurrences of the error? In your example there are two \cites and both contain invisible characters: The first three, the second four. Copy and paste your text to w3c.github.io/xml-entities/unicode-names.html and search for U+200d or zero width. (edit: The \end{document} also contains unwanted zero-width joiners.) – moewe Feb 11 at 13:57
• To get rid of the weird character �, as @moewe points out, you can (1) "Cut" the text ferromagnetic phases (\‍‍‍cite{gattacceca2003magnetic}). from your line 296 of your tex file, (2) "Paste" it on some minimal text editor like Notepad in Windows (or browser address/search bar), (3) remove any unusual character like � or anything that you between  and cite, (4) "Copy" that text again, and (5) "Paste" it back to your tex file. In that way you will be able to see what went wrong... and hopefully surpass that error. – Partha D. Feb 11 at 14:16