1. “Piezoelectricity”;Cady,1946
2. Piezo-Electric and Allied Phenomena in Rochelle Salt
3. Thurnauer H. and Deaderick, J., U.S. Patent 2, 429, 588, Oct. 21, 1947; field Oct. 2, 1941.
4. Wainer, E. and Salomon, A. N. Titanium Alloy Mfg. Co., Electrical Report No. 8 (Sept. 17, 1942); Electrical Report No. 9 (Jan. 9, 1943).