# Multiple references separated by semi-colon

The following is in the preamble I "inherited":

\documentclass[a4paper,12pt]{book}
\usepackage{amsmath, amsthm, amssymb}
\usepackage{fancyhdr}
\pagestyle{fancy}
\renewcommand{\footrulewidth}{0.1pt} % for lower line
\fancyfoot[C]{\thepage}

\usepackage{fancybox}

\usepackage{xcolor}
\usepackage{framed}

\numberwithin{equation}{section} % numbering according to the section
\bibliographystyle{plain} %Choose a bibliograhpic style

\usepackage{color}

%\parindent0em
\parskip1ex

In my .tex file, for each reference I state, for instance: "as reported in \citep{schum98,berg90,tom90}". The pdf output "[Schuman, 1998, Berg, 1990, Tomaven, 1990]". As you may notice, such a listing is awkward. How could I separate the data belonging to a specific author by a semi-colon from the data belonging to other authors, as in "[Schuman, 1998; Berg, 1990; Tomaven, 1990]". Note that a large portion of the .tex document has been written, and I would prefer the option of just changing the preamble.

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With that preamble you won't get an author-year citation scheme. –  egreg Apr 25 '12 at 13:16
I solved it by adding \usepackage[semicolon]{natbib}. Thanks for pointing out the missing natbib. –  boy Apr 25 '12 at 13:26
@boy: once the software allows you to do so, you should post your resolution (the comment above) as an answer. –  Willie Wong Apr 25 '12 at 14:58