Using natbib and thebibliography

Question

I'm trying to create a citation like:

The books (Charles, 1985; Smith, 1989) are great.

by using package natbib and

\begin{thebibliography}{99}

\bibitem[(Charles, 1985)]{Charles85}

\bibitem[(Smith, 1989)]{Smith89}

\end{thebibliography}{}

But the command \citep{Charles85,Smith89} does not seem to work.

Answer 1

natbib needs the author and year information in the optional argument of \bibitem to be in a special format so it can be parsed. natbib.sty explains the possible formats in a comment

 % If author-year citations are selected, \bibitem must have one of the
 %   following forms:
 %   \bibitem[Jones et al.(1990)]{key}...
 %   \bibitem[Jones et al.(1990)Jones, Baker, and Williams]{key}...
 %   \bibitem[Jones et al., 1990]{key}...
 %   \bibitem[\protect\citeauthoryear{Jones, Baker, and Williams}{Jones
 %       et al.}{1990}]{key}...
 %   \bibitem[\protect\citeauthoryear{Jones et al.}{1990}]{key}...
 %   \bibitem[\protect\astroncite{Jones et al.}{1990}]{key}...
 %   \bibitem[\protect\citename{Jones et al., }1990]{key}...
 %   \harvarditem[Jones et al.]{Jones, Baker, and Williams}{1990}{key}...

The format used in the question

\bibitem[(Charles, 1985)]{Charles85}

is not among the supported formats. The simplest way to make the information digestible for natbib is probably by dropping the parentheses to make it read

\bibitem[Charles, 1985]{Charles85}

Alternatively, you could use the format that natbib's standard .bst files use

\bibitem[Charles(1985)]{Charles85}

In total

\documentclass[british]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage{natbib}


\begin{document}
\citep{Charles85,Smith89}

\begin{thebibliography}{99}

\bibitem[Charles, 1985]{Charles85} Anne Charles: \emph{Title}. 1985

\bibitem[Smith, 1989]{Smith89} Jane Smith: \emph{Another Title}. 1989

\end{thebibliography}
\end{document}

---

That said, it is usually more comfortable to use .bib files and BibTeX (or biblatex and Biber: bibtex vs. biber and biblatex vs. natbib) instead of a manual thebibliography. Entries can be re-used and re-styled more easily and BibTeX (or Biber) takes care of sorting.