1. 4E. Cerwenka , thesis , Tech. Hochsch. Graz (1951); cited in Paul Schwarzkopf and Richard Kieffer (in collaboration with Werner Leszynski and Fritz Benesovsky), Refractory Hard Metals-Borides, Carbides, Nitrides, and Silicides, pp. 325 and 328. Macmillan Co., New York, 1953. 447 pp.Ceram. Abstr., 1954, January, p. 10j.