\begin{thebibliography}{} \bibitem[OPS98]{OPS98} J. Opgenorth, W. Plesken, and T. Schulz. \newblock Crystallographic Algorithms and Tables. \newblock {\em Acta Cryst A} 54, 517--531 (1998). \end{thebibliography}
\begin{thebibliography}{} \bibitem[OPS98]{OPS98} J. Opgenorth, W. Plesken, and T. Schulz. \newblock Crystallographic Algorithms and Tables. \newblock {\em Acta Cryst A} 54, 517--531 (1998). \end{thebibliography}