harvard bibliography, improper alphabetic constant

Question

I am trying to make a Harvard style bibliography, using bibtex and the package natbib, for a journal which requires it, but the online facility I have to use won't take the .bib to process it. So I have cut and paste the contents of the .bbl file where the input command for the bibliography would have been. This processes runs once quite happily, but you have to do it twice, and the second time, I get the error:

********
./filename: Improper alphabetic constant
<to be read again>
                  \protect
l.7 blah\cite{paper1,paper2}
?
and typing h for help gives
A one-character control sequence belongs after a ` mark.
So I am essentially inserting \0 here.
******

Now, if I hit q for batchmode I get a the .pdf I want, but the online facility will not allow me to do that and it just fails. My own system reproduces the error, so it is not a problem with their facility. I am using natbib 8.31 and TeXShop 3.62

test file:

\documentclass[12pt,a4paper]{article}

\usepackage{natbib} %harvard style

\begin{document}

blah\cite{paper1,paper2}

\bibliographystyle{agsm}
%\bibliography{testbib}

\begin{thebibliography}{xx}

\harvarditem{Auth}{{2001}{\em a}}{paper1}
Auth, P.~J.  \harvardyearleft {2001}{\em a}\harvardyearright , `{paper1}', {\em {Journal 1}} {\bf {11}}({5}),~{417--436}.

\harvarditem{Auth}{{2001}{\em b}}{paper2}
Auth, P.~J.  \harvardyearleft {2001}{\em b}\harvardyearright , `{paper2}', {\em {Journal 2}} {\bf
  {1}}({1}),~{3--67}.

\end{thebibliography}
\end{document}

Answer 1

natbib does not like the format of the years in

\harvarditem{Auth}{{2001}{\em a}}{paper1}

Either manually change them to

\harvarditem{Auth}{2001a}{paper1}

or switch from natbib to harvard.

---

After playing around with the MWE in Mico's answer and comparing his .bbl with yours, I can't help but notice that yours features quite a bit more curly brackets than the one produced from a usual .bib file.

My current working hypothesis is that your .bib file contains too many curly brackets. Did you wrap fields in two pairs as in

journal = {{Journal 1}},
volume  = {{1}},

---

\documentclass[12pt,a4paper]{article}
\usepackage{harvard} %harvard style

\begin{document}
blah\cite{paper1,paper2}

\begin{thebibliography}{xx}
\harvarditem{Auth}{{2001}{\em a}}{paper1}
Auth, P.~J.  \harvardyearleft {2001}{\em a}\harvardyearright , `{paper1}', {\em {Journal 1}} {\bf {11}}({5}),~{417--436}.

\harvarditem{Auth}{{2001}{\em b}}{paper2}
Auth, P.~J.  \harvardyearleft {2001}{\em b}\harvardyearright , `{paper2}', {\em {Journal 2}} {\bf
  {1}}({1}),~{3--67}.
\end{thebibliography}
\end{document}

or

\documentclass[12pt,a4paper]{article}
\usepackage{natbib}

\begin{document}
blah\cite{paper1,paper2}

\begin{thebibliography}{xx}
\harvarditem{Auth}{2001{\em a}}{paper1}
Auth, P.~J.  \harvardyearleft {2001}{\em a}\harvardyearright , `{paper1}', {\em {Journal 1}} {\bf {11}}({5}),~{417--436}.

\harvarditem{Auth}{2001{\em b}}{paper2}
Auth, P.~J.  \harvardyearleft {2001}{\em b}\harvardyearright , `{paper2}', {\em {Journal 2}} {\bf
  {1}}({1}),~{3--67}.
\end{thebibliography}
\end{document}

Answer 2

First off, the bbl file seems to have some errors. I assume they crept in when somebody (you?) applied some changes by hand to the contents of the bbl file. (For sure, they would not appear to have been generated by LaTeX or the natbib citation management package.)

For instance,

\harvarditem{Auth}{{2001}{\em a}}{paper1}

is wrong. It should be

\harvarditem{Auth}{2001{\em a}}{paper1}

Similarly, you need to replace

\harvarditem{Auth}{{2001}{\em b}}{paper2} 

with

\harvarditem{Auth}{2001{\em b}}{paper2}

Second, once you've copied the contents of the bbl file into the tex file (and deleted the \bibliography statement), you should also delete (or comment out) the directives \usepackage{natbib} and \bibliographystyle{agsm} statements. Finally, rerun LaTeX on the newly-modified tex file; it should compile correctly, making it ready to be uploaded to the publisher's website.

---

Just for completeness, here's the code that gives rise to the bbl contents mentioned above.

\RequirePackage{filecontents}
\begin{filecontents}{mybib.bib}
@article{paper1,
  author = "Perri Jane Auth", title = "Amiable Thoughts",
  journal = "Circularity Today", year = 2001, volume = 1, number = 2, pages = "3-4",
}
@article{paper2,
  author = "Perri Jane Auth", title = "Darker Thoughts",
  journal= "Circularity Today", year = 2001, volume = 5, number = 6, pages = "7-8",
}
\end{filecontents}

\documentclass{article}
\usepackage{natbib}
\bibliographystyle{agsm}

\begin{document}
\cite{paper1,paper2}
\bibliography{mybib}
\end{document}

The resulting bbl file should have the following contents:

\begin{thebibliography}{xx}

\harvarditem{Auth}{2001{\em a}}{paper1}
Auth, P.~J.  \harvardyearleft 2001{\em a}\harvardyearright , `Amiable
  thoughts', {\em Circularity Today} {\bf 1}(2),~3--4.

\harvarditem{Auth}{2001{\em b}}{paper2}
Auth, P.~J.  \harvardyearleft 2001{\em b}\harvardyearright , `Darker thoughts',
  {\em Circularity Today} {\bf 5}(6),~7--8.

\end{thebibliography}

The typeset bibliography should look like this: