[tex-k] Latex warning: citation...undefined

[Christoph Bier]

i'm using WEB2C 7.3.1 (bibtex 0.99c) and cannot create .bbl resp. a 
correct .aux. doing
'latex file.tex' results in warnings like that:

LaTeX Warning: Citation `gehalt:handb:8' on page 1 undefined on input 
line 22.

examplary file.tex looks like this:

\documentclass[a4paper,12pt]{article}

\usepackage{german}
\usepackage[latin1]{inputenc}
\usepackage{setspace}
\onehalfspacing

\usepackage{geometry}
\geometry{left=3.5cm,right=2.5cm}

\usepackage[german]{varioref}

\usepackage[bf,footnotesize,nooneline,sf]{caption}

\pagestyle{headings}

\begin{document}

%content
...\cite{gehalt:handb:8}...

\bibliographystyle{unsrt}
\bibliography{/home/chris/diplom/diplomarbeit/bibliographie/bibfile2}

\end{document}

i don't know where a mistake could be. maybe i use old style files as 
mentioned in btxdoc...
but how can i check this?
i used the way of citation like described in a latex-book. in btxdoc i 
cannot find anything
  appropriate - except the part with the old style files. i also checked 
the tex-k archive
unsuccesfully and browsed the web the last three weeks.
can somebody help me?

greetings,
christoph