1. Britvec, S.J., 1963 “Elastic Buckling of Pin-jointed Frames”, Int. J. Mech. Sci. Vol 5, pp. 447–461.
2. Op. cit.
3. See also Theorem 5, Ref. 15, page 74.
4. Britvec, S.J., 1963 “Elastic Buckling of Pin-jointed Frames”, Int. J. Mech. Sci. Vol 5, pp. 447–460.
5. “The Stability of Elastic Systems” by S.J. Britvec, Pergamon Press, Oxford, New York, 1973 (Chapter 3). See also, Test 1, Section 1.2, pp. 20, 21.