1. J. R. Vig, J. W. Lebus andR. L. Filler, Proceedings of the 31st Annual Symposium on Frequncy Control. Fort Monmouth, New Jersey, 1977 (Electronic Industries Association, Washington, DC, 1977) p. 131.
2. J. Appl. Phys. 35 (1964) 1362.
3. Y. Sekiguchi andH. Funakubo,J. Mater. Sci. 15 (1980) 3066.
4. H. Fukuyo andN. Oura, Proceedings of the 30th Annual Symposium on Frequency Control, Fort Monmouth, New Jersey, 1976 (Electronic Industries Association, Washington, D C, 1976) p. 254.
5. P. Maitre, Th�se de Doctorat Universit� de Besancon, France (1979).