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2. Takagi, T.: Z. Phys. D - Atoms, Molecules and Clusters 3, 271 (1986)
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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
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