1. The Piezo Electric Effect in the Composite Rochelle Salt Crystal
2. A. M. Nicholson, U. S. Patents: Nos. 1,495,429; 1,525,823; 1,655,625; 2,135,852; 2,212,845.
3. R. Nacken, “Report on the Research Contract for Synthesis of Oscillator Crystals,” Captured German Report RDRDC/13/18. Also—Office of Technical Services Reports, PB-6498, PB-18,784, PB-28,897, and others, Dept. of Commerce, Washington, D. C.