1. V. I. Feodos’ev, Strength of Materials (Nauka, Moscow, 1979) [in Russian].
2. S. P. Timoshenko, Strength of Materials, Part II, Advanced Theory and Problems (D. Van Nostrand, Princeton, 1955; Fizmatgis, Moscow, 1965).
3. A. N. Dinnik, The Stability of Elastic Systems (ONTI, Moscow, 1935) [in Russian].
4. Sh. E. Mikeladze, New Methods for Integrating Differential Equations and Their Applications to Elasticity Problems (Gostekhizdat, Moscow-Leningrad, 1951) [in Russian].
5. L. Collatz, Eigenvalue Problems with Technical Applications (Chelsea, New York, 1948; Nauka, Moscow, 1968).