1. P. K. Rol, J. M. Fluit, F. P. Viehböck, M. deJong: In Proc. 4th Int. Conf. Phen. Ion. Gases, Uppsala, ed. by N. R. Nilsson (North-Holland, Amsterdam 1959) p. 257
2. V. A. Molchanov, V. G. Tel'kovskii, V. M. Chickerov:Sov. Phys.-Doklady 6, 3, 222 (1961)
3. O. Almén, G. Bruce: Nucl. Instrum. Methods 11, 257 (1961)
4. J. Stark, G. Wendt: Ann. Phys. (Leipzig) 38, 921 (1912)
5. J. Stark, G. Wendt: Ann. Phys. (Leipzig) 38, 941 (1912)