O.C. Zienkiewicz and R.W. Gerstner, "The Method of Interface Stress Adjustment and Its Uses in the Solution of Some Plane Elasticity Problems,"Int. J. Mech. Sci., Vol. 2 (1961), p. 267.
2.
S. Timoshenko and J.N. Goodier, Theory of Elasticity, McGraw-Hill, New York (1951).