我正在使用期刊出版物所示的 .bst 文件 (theapa.bst) 撰写论文。
这是一个简单的例子（main.tex）来重现我所面临的问题：
\documentclass[twoside,11pt]{article}
\usepackage{jair, theapa, rawfonts}
\usepackage{natbib}
\jairheading{1}{1993}{1-15}{6/91}{9/91}
\ShortHeadings{Test}
{}
\firstpageno{1}
\begin{document}
\title{Test}
\author{}
\maketitle
\begin{abstract}
Paper~\cite{Zhang18}
\end{abstract}
\vskip 0.2in
\bibliography{matching}
\bibliographystyle{theapa}
\end{document}
以下是.bib文件（matching.bib）：
@inproceedings{Zhang18,
author = {Yuzhe Zhang and Kentaro Yahiro and Toshiya Sato},
title = {Strategyproof and Fair Matching Mechanism for Union of Symmetric {M}-convex
Constraints},
booktitle = {Proceedings of the 27th International Joint Conference on
Artificial Intelligence (IJCAI-18)},
pages = {590--596},
year = {2018},
}
然后就会出现如下错误：
main.bbl line 4
Undefined control sequence. et~al.}{2018}]{Zhang18}
日志文件是：
This is pdfTeX, Version 3.14159265-2.6-1.40.21 (TeX Live 2020) (preloaded format=pdflatex 2020.5.17) 7 NOV 2020 14:33
entering extended mode
restricted \write18 enabled.
%&-line parsing enabled.
**main.tex
(./main.tex
LaTeX2e <2020-02-02> patch level 5
L3 programming layer <2020-05-14>
(/usr/local/texlive/2020/texmf-dist/tex/latex/base/article.cls
Document Class: article 2019/12/20 v1.4l Standard LaTeX document class
(/usr/local/texlive/2020/texmf-dist/tex/latex/base/size11.clo
File: size11.clo 2019/12/20 v1.4l Standard LaTeX file (size option)
)
\c@part=\count167
\c@section=\count168
\c@subsection=\count169
\c@subsubsection=\count170
\c@paragraph=\count171
\c@subparagraph=\count172
\c@figure=\count173
\c@table=\count174
\abovecaptionskip=\skip47
\belowcaptionskip=\skip48
\bibindent=\dimen134
) (./jair.sty
Document Style `jair' -- May 1993.
\aftertitskip=\skip49
\beforetitskip=\skip50
\interauthorskip=\skip51
\aftermaketitskip=\skip52
) (./theapa.sty
Package: theapa 1997/06/03 Version 3.0 APA Citation Style
LaTeX Info: Redefining \cite on input line 122.
LaTeX Info: Redefining \nocite on input line 417.
\bibleftmargin=\skip53
\bibparsep=\skip54
)
(/usr/local/texlive/2020/texmf-dist/tex/latex/tools/rawfonts.sty
Package: rawfonts 1994/05/08 Low-level LaTeX 2.09 font compatibility
(/usr/local/texlive/2020/texmf-dist/tex/latex/tools/somedefs.sty
Package: somedefs 1994/06/01 v0.03 Toolkit for optional definitions
)
LaTeX Font Info: Trying to load font information for U+lasy on input line 49
.
(/usr/local/texlive/2020/texmf-dist/tex/latex/base/ulasy.fd
File: ulasy.fd 1998/08/17 v2.2e LaTeX symbol font definitions
))
(/usr/local/texlive/2020/texmf-dist/tex/latex/natbib/natbib.sty
Package: natbib 2010/09/13 8.31b (PWD, AO)
\bibhang=\skip55
\bibsep=\skip56
LaTeX Info: Redefining \cite on input line 694.
LaTeX Info: Redefining \citeauthor on input line 712.
LaTeX Info: Redefining \citeyear on input line 735.
\c@NAT@ctr=\count175
)
(/usr/local/texlive/2020/texmf-dist/tex/latex/l3backend/l3backend-pdfmode.def
File: l3backend-pdfmode.def 2020-05-05 L3 backend support: PDF mode
\l__kernel_color_stack_int=\count176
\l__pdf_internal_box=\box45
)
(./main.aux)
\openout1 = `main.aux'.
LaTeX Font Info: Checking defaults for OML/cmm/m/it on input line 11.
LaTeX Font Info: ... okay on input line 11.
LaTeX Font Info: Checking defaults for OMS/cmsy/m/n on input line 11.
LaTeX Font Info: ... okay on input line 11.
LaTeX Font Info: Checking defaults for OT1/cmr/m/n on input line 11.
LaTeX Font Info: ... okay on input line 11.
LaTeX Font Info: Checking defaults for T1/cmr/m/n on input line 11.
LaTeX Font Info: ... okay on input line 11.
LaTeX Font Info: Checking defaults for TS1/cmr/m/n on input line 11.
LaTeX Font Info: ... okay on input line 11.
LaTeX Font Info: Checking defaults for OMX/cmex/m/n on input line 11.
LaTeX Font Info: ... okay on input line 11.
LaTeX Font Info: Checking defaults for U/cmr/m/n on input line 11.
LaTeX Font Info: ... okay on input line 11.
Package natbib Warning: Citation `Zhang18' on page 1 undefined on input line 20
.
(./main.bbl
! Undefined control sequence.
\NAT@tmp ->\protect \BCAY
{Zhang, Yahiro,\ \BBA \ Sato}{Zhang et~al.}{2018}
l.4 et~al.}{2018}]{Zhang18}
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.
! Undefined control sequence.
<argument> ...ter \NAT@ifcmd \NAT@tmp (@)(@)\@nil
{Zhang18}
l.4 et~al.}{2018}]{Zhang18}
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.
)
Package natbib Warning: There were undefined citations.
[1{/usr/local/texlive/2020/texmf-var/fonts/map/pdftex/updmap/pdftex.map}
]
(./main.aux) )
Here is how much of TeX's memory you used:
1010 strings out of 480480
13548 string characters out of 5899675
248169 words of memory out of 5000000
17058 multiletter control sequences out of 15000+600000
548022 words of font info for 83 fonts, out of 8000000 for 9000
1141 hyphenation exceptions out of 8191
23i,5n,25p,218b,165s stack positions out of 5000i,500n,10000p,200000b,80000s
{/usr/local/texlive/2020/texmf-dist/fonts/enc/dvips/cm-super/cm-s
uper-ts1.enc}</usr/local/texlive/2020/texmf-dist/fonts/type1/public/amsfonts/cm
/cmbx10.pfb></usr/local/texlive/2020/texmf-dist/fonts/type1/public/amsfonts/cm/
cmbx12.pfb></usr/local/texlive/2020/texmf-dist/fonts/type1/public/amsfonts/cm/c
mr10.pfb></usr/local/texlive/2020/texmf-dist/fonts/type1/public/amsfonts/cm/cmr
8.pfb></usr/local/texlive/2020/texmf-dist/fonts/type1/public/amsfonts/cm/cmti10
.pfb></usr/local/texlive/2020/texmf-dist/fonts/type1/public/cm-super/sfrm0800.p
fb>
Output written on main.pdf (1 page, 66903 bytes).
PDF statistics:
33 PDF objects out of 1000 (max. 8388607)
23 compressed objects within 1 object stream
0 named destinations out of 1000 (max. 500000)
1 words of extra memory for PDF output out of 10000 (max. 10000000)
此外，当我引用以下文章时，
@article{gibbard:1973,
title={Manipulation of Voting Schemes: A General Result},
author={Gibbard Allan},
journal={Journal of the Econometric Society},
pages={587--601},
year={1973},
publisher={JSTOR},
}
出现了错误。
You can't pop an empty literal stack for entry gibbard:1973
while executing---line 2867 of file theapa.bst
(There was 1 error message)
为什么会发生这种情况？