Thanks everybody, we have got it :)
Just to summarize it for the archive:
At my Linux distribution (SuSE6.4) there are 3 bst files in
/usr/share/texmf/bibtex/bst/natbib
abbrvnat.bst (Auther-Year & numeric citation)
plainnat.bst (numeric citation only)
unsrtnat.bst (Auther-Year & numeric citation)
As a style sheet I used:
/usr/share/texmf/tex/latex/natbib/natbib.sty
There is some documentation in natbib.sty which should clarify magic lines
like
\usepackage[round,comma]{natbib}
As lyx only seems to use \cite for citing it might be useful to redefine it to
\renewcommand{\cite}{\citet}
or similar.
Guess that's the little lesson we learned yesterday :)
oliver
--
Ingenieure Kellermann, Voigt, Hoepfl, Eichler, Weidner und Klinger
DSP Solutions http://www.dspsolutions.de