1. Atanasoff and HartPhy. Rev., 1941,59, 85.
2. Lucas and BiquardJour. d. Phys., 1932,3, 464.
3. Debye and SearsProc. Nat. Acad. Sci., 1932,18, 409.
4. LoveA Treatise on the Mathematical Theory of Elasticity, p. 298.
5. VoigtLehrbuch der Kristallphysik, 1910.