1. Takagi, T., Yamada, I., Kunori, M., Kobiyama, S.: Proceedings of the 2nd International Conference on Ion Sources. pp. 790?795. Vienna: Österreichische Studiengesellschaft für Atomenergie GmbH 1972
2. Takagi, T.: Z. Phys. D ? Atoms, Molecules and Clusters3, 271 (1986)
3. Becker, E.W., Bier, K., Henkes, W.: Z. Phys.146, 333 (1956)
4. Stein, G.D.: In: Proceedings of the International Ion Engineering Conference ? ISIAT ?83 & IPAT ?83 ? Kyoto. Takagi, T. (ed.), pp. 1165?1176B. Tokyo: Inst. Elect. Eng. Japan 1983
5. Yamada, I.: ibid. pp. 1177?1192A