1. V. G. Babskii, N. D. Kopachevskii, A. D. Myshkis, L. A. Slobozhanin, and A. D. Tyuptsov, Hydrodynamics of Weightlessness [in Russian], Nauka, Moscow (1976), p. 504.
2. N. N. Moiseev and V. V. Rumyantsev, Dynamics of a Body with Cavities Containing a Liquid [in Russian], Nauka, Moscow (1965), p. 439.
3. E. F. Beckenbach and R. Bellman, Inequalities, Springer, Berlin (1965).