1. F. S. Lapteva and B. V. Ershler, At. Energ., No. 4, 63 (1956).
2. N. V. Pleshivtsev, Cathodic Sputtering [in Russian], Atomizdat, Moscow (1968).
3. I. Lifshitz, et al., At. Energ.,6, No. 4, 391 (1959).
4. M. Rogers and I. Adam, J. Nucl. Mater.,6, No. 2, 182 (1962).
5. M. Rogers, ibid.,22 No. 1, 103 (1967).