1. K. Wada, Report of National Pearl Research Institute. 8, (1662) 1003.
2. H. Kugisawa, T. Aita, J. of Japan Society of Applied Physics. (Oyoo Butsuri) 53, No. 10, (1984) 895.
3. H. Kugisawa, T. Aita, 55, No. 5 (1986) 499.
4. Science Publication series of Idemitsu;I. Sunagawa,1977
5. Encyclopedia of Science & Technology. Part 1, p51 ?Aragonite?, Part 9, p899 ?Pearl?. (Mcgraw Hill Inc., New York. 1960)