1. (1) Bolotin, V. V., “Nonconservative Problems of the Theory of Elastic Stabilities, Pergamon press (1963).
2. (2) Ziegler, H., “Principles of Structural Stability”, Blaisdell Publishing Company, A Division of Ginn and Company (1968).
3. (4) Leipholz, H., “Stability of elastic systems”, The Universities Press, Belfast, Samsom-Sijthoff, Alphen aan den Rijn (1980).