\bibitem{skorupa} W. Skorupa, V. Heera, Y. Pacaud, H. Weishart in: F. Priolo, J. K. N. Lindner, A. Nylandsted Larsen, J. M. Poate (Eds.). New Trends in Ion Beam Processing of Materials. Europ. Mater. Res. Soc. Symp. Proc. 65 Part 1. Elsevier Amsterdamm (1977) 114.
\bibitem{reiber} J. K. N. Lindner, W. Reiber, B. Stritzker. Mater. Sci. Forum 264-268 (1998) 215-218.
\end{thebibliography}
\bibitem{skorupa} W. Skorupa, V. Heera, Y. Pacaud, H. Weishart in: F. Priolo, J. K. N. Lindner, A. Nylandsted Larsen, J. M. Poate (Eds.). New Trends in Ion Beam Processing of Materials. Europ. Mater. Res. Soc. Symp. Proc. 65 Part 1. Elsevier Amsterdamm (1977) 114.
\bibitem{reiber} J. K. N. Lindner, W. Reiber, B. Stritzker. Mater. Sci. Forum 264-268 (1998) 215-218.
\end{thebibliography}