1. E.E. Sechler, Elasticity in Engineering, Dover ( 1968 ), p. 130.
2. S. Timoshenko, Strength of Materials, Part I, Elementary Theory and Problems, 3rd edit. Van Nostrand (1955), p. 170.
3. S.G. Lekhnitskii, Anisotropic Plates, translated by S. W. Tsai and T. Cheron, Gordon and Breach (1968), p. 57.