# Natbib doesn't add a's and b's to same-author-same-year references

I am using natbib with bibtex8 in lyx to get my references sorted. It all seems to work fine except that natbib does not properly deal with "same-author-same-year" references. Rather than giving me: (Keiser 2005a,b) it gives me (Keiser 2005,?).

I am using a custom *.bst file, so I think that the problem might be in the bst file which can be downloaded from here. An example of my *.bib items is given below.

@article{Keiser2005b,
author = {Keiser, Jennifer and Maltese, Michael F and Erlanger, Tobias E and Bos, Robert and Tanner, Marcel and Singer, Burton H and Utzinger, Jurg},
journal = {Acta Tropica},
number = {1},
pages = {40--57},
title = {{Effect of irrigated rice agriculture on Japanese encephalitis, including challenges and opportunities for integrated vector management.}},
volume = {95},
year = {2005}
}

@article{Keiser2005,
author = {Keiser, Jennifer and Singer, Burton H and Utzinger, Jurg},
journal = {The Lancet infectious diseases},
number = {11},
pages = {695--708},
title = {{Reducing the burden of malaria in different eco-epidemiological settings with environmental management: a systematic review}},
volume = {5},
year = {2005}
}


Here is an example that generates the problem:

\documentclass[british]{report}
\renewcommand{\familydefault}{\rmdefault}
\usepackage[T1]{fontenc}
\usepackage[a4paper]{geometry}
\geometry{verbose,tmargin=1.5in,bmargin=1.4in,lmargin=1.5in,rmargin=1in}
\usepackage{fancyhdr}
\pagestyle{fancy}
\setcounter{secnumdepth}{0}
\setcounter{tocdepth}{3}
\setlength{\parindent}{1.5cm}
\usepackage[authoryear]{natbib}
\usepackage{babel}
\begin{document}
bla bla \citep{Keiser2005,Keiser2005b} bla bla

\bibliographystyle{Naresuan_style_nat}
\bibliography{library.bib}

\end{document}


Any help would be greatly appreciated!

• Welcome to TeX.SX! You can have a look at our starter guide to familiarize yourself further with our format. Do you know what bibliography style you use? Is it compatible with natbib? Have you processed the document itself 3 times after running bibtex (this is important, it's not 2 times, it's 3 times for natbib)? I'm not sure how does all this work in LyX, but these are the typical problems people have with natbib in LaTeX... – yo' Mar 17 '15 at 9:41
• @yo' Thanks for your suggestion but it doesn't seem to be the problem. I have edited the question a little bit so that it contains a hopefully proper example. – Robbie Mar 17 '15 at 11:18

\usepackage{chicago}