[Tex/LaTex] Natbib+harvard.bst: papers in same year listed in the wrong order

bibtexnatbibsorting

I have a bibliography in which a particular author wrote two papers in the same year. Bibtex is sorting them alphabetically by title, but I want them listed chronologically. (So in the example below 'universal grammar' should precede 'English as a formal language'.) What's the appropriate way to flip the order?

MWE:

\documentclass{article}
\usepackage{natbib}
\begin{document}

... formal semantics in the  Montagovian tradition \citep{montague1970aug,montague1970befl,montague1973ptq}. 

\bibliographystyle{harvard}
\bibliography{test}
\end{document}

This generates the text 'formal semantics in the Montagovian tradition (Montague, 1970b,a, 1973)' whereas I actually want '1970a,b,1973'.

test.bib file for MWE:

@incollection{montague1973ptq,
  title={The proper treatment of quantification in ordinary {English}},
  author={Montague, Richard},
  booktitle={Approaches to natural language},
  editor={Hintikka, K. Jaakko J. and Moravcsik, Julius M.E. and Suppes, Patrick},
  pages={221--242},
  year={1973},
  publisher={Dordrecht}
}

@article{montague1970aug,
  title={Universal grammar},
  author={Montague, Richard},
  journal={Theoria},
  volume={36},
  number={3},
  pages={373--398},
  year={1970},
  publisher={Blackwell Synergy}
}

@incollection{montague1970befl,
  title={English as a formal language},
  author={Montague, Richard},
  booktitle={Linguaggi nella Societa e nella Tecnica},
  editor={Visentini, Bruno and others},
  publisher={Edizioni di Comunità},
  pages={189--224},
  year={1970}
}

Best Answer

Since the sorting order is 1. year, 2. lexicographic by title, you can supply a mock argument to the title: write this in your LaTeX document

\newcommand{\mockalph}[1]{}

and insert the titles respectively as

title={{\mockalph{bbbbb}}Universal grammar},

title={{\mockalph{ccccc}}English as a formal language},

so that the ordering will be with respect to bbbbb and ccccc, which won't be printed anyway.

Why not aaaaa for the first? Well, if you discover a book by Montague that's been printed before "Universal grammar", …

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