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2. A.J. Birkle, R. P. Wei, and G. F. Pellissier:Trans. ASM, 1966, vol. 54, pp. 981–90.
3. L. F. Porter: unpublished research, U.S. Steel Research Laboratory, Monroeville, PA, 1970.
4. I.J. Hauser, M. G. H. Wells, and I. Perlmutter:J. Vac. Sci. Tech., 1972, vol. 9, pp. 1339–41.
5. L. F. Porter: discussion to above paper,ibid, pp. 1340–43.