%&LaTeX
\documentclass{article}

\usepackage[latin1]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{textcomp}

\begin{document}

\begin{thebibliography}{1}

\bibitem{Geiger1984} Geiger, C. (1984). \textit{Graureiher Ardea cinerea und Fischbestand in Flie{\ss}gew{\"a}ssern} (Vol. 81).

\end{thebibliography}

\end{document}

