I am trying to compile my references using the plain bibliography style but I keep getting an 'undefined control sequence' error. This is the full error:

    ! Undefined control sequence.
<argument> \citeauthoryear 
                           {Riess\ \BOthers {.}}{Riess\ \BOthers {.}}{{\APAC...
l.35 ...xpansion of the Universe \cite{Riess_1998}
                                                  [1][2], by studying distan...
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.

My references.bib file is

    doi = {10.1086/300499},
    url = {https://doi.org/10.1086%2F300499},
    year = {1998},
    month = {},
    publisher = {{IOP} Publishing},
    volume = {116},
    number = {3},
    pages = {1009--1038},
    author = {Adam G. Riess and Alexei V. Filippenko and Peter Challis and Alejandro Clocchiatti and Alan Diercks and Peter M. Garnavich and Ron L. Gilliland and Craig J. Hogan and Saurabh Jha and Robert P. Kirshner and B. Leibundgut and M. M. Phillips and David Reiss and Brian P. Schmidt and Robert A. Schommer and R. Chris Smith and J. Spyromilio and Christopher Stubbs and Nicholas B. Suntzeff and John Tonry},
    title = {Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant},
    journal = {The Astronomical Journal},
    abstract = {We present spectral and photometric observations of 10 Type Ia supernovae...}

My bbl file is


\bibitem [\protect \citeauthoryear {%
\ \protect \BOthers {.}}{%
\ \protect \BOthers {.}}{%
{\protect \APACyear {1998}}%
\APACinsertmetastar {%
Riess, A\BPBI G.%
, Filippenko, A\BPBI V.%
, Challis, P.%
, Clocchiatti, A.%
, Diercks, A.%
, Garnavich, P\BPBI M.%
\BDBL {}Tonry, J.%
{\BBOQ}\APACrefatitle {Observational Evidence from Supernovae for an
  Accelerating Universe and a Cosmological Constant} {Observational evidence
  from supernovae for an accelerating universe and a cosmological
\APACjournalVolNumPages{The Astronomical Journal}{116}{3}{1009--1038}.
\begin{APACrefURL} \url{https://doi.org/10.1086%2F300499} \end{APACrefURL}
\begin{APACrefDOI} \doi{10.1086/300499} \end{APACrefDOI}


My main .tex file is

In 2011, Perlmutter, Schmidt and Reiss were awarded the Nobel Prize in Physics for their discovery of the accelerating expansion of the Universe \cite{Riess_1998}



Any help would be greatly appreciated! Thank you!

  • Welcome to TeX.SE. Did you recently change the argument of \bibliographystyle? The reason I ask is that it looks like the contents of the bbl file were produced on the basis of the apacite bibliography style. Please advise. – Mico Mar 17 at 5:21
  • Yes I was using apacite but it wasn't in the format that I wanted so I changed it – Lisa Mar 17 at 13:35

After changing the argument of \bibliographystyle from apacite to plain -- and removing the instruction \usepackage{apacite} too, right? -- the code in the .bbl file no longer "makes sense" to LaTeX, given that the bbl file was created when the apacite package was still loaded. This is the source of the error messages you're getting.

What you need to do is (a) delete all auxiliary files, including the .bbl file, and (b) perform a full recompile cycle -- LaTeX, BibTeX, and LaTeX twice more.

  • 1
    I tried this and it worked! Thank you so much!!! – Lisa Mar 17 at 15:48

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