A convention sometimes used in physics journals is to "collapse" a group of related citations into a single entry in the bibliography. BibTeX, by default, can't cope with this arrangement, but the mcite package deals with the problem.
The package overloads the \cite command to recognise a
"*" at the start of a key, so that citations of the form
\cite{paper1,*paper2}
appear in the document as a single citation, and appear arranged
appropriately in the bibliography itself. You're not limited to
collapsing just two references. You can mix "collapsed" references
with "ordinary" ones, as in
\cite{paper0,paper1,*paper2,paper3}
Which will appear in the document as 3 citations "[4,7,11]"
(say) - citation '4' will refer to paper 0, '7' will refer to a
combined entry for paper 1 and paper 2, and '11' will refer to
paper 3.
You need to make a small change to the bibliography style (.bst) file you
use; the mcite package documentation tells you how to do that.
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=mcite