1. Annals of Mathematics Studies;G. Pólya ,1951
2. Timoshenko S. History of Strength of Materials (McGraw-Hill, New York, 1953).
3. Mikhlin S.G. Variational methods in Mathematical Physics (Pergamon Press, Oxford, 1964).
4. Payne L.E. "Some isoperimetric inequalities in the torsion problem for multiply connected regions", in: Studies in Mathematical Analysis and Related Topics: Essays in Honor of George Pólya, ed. by Szegö G. et al., 270-280 (Stanford Univ. Press, Stanford, 1962).
5. de Saint-Venant B. "Memoire sur la torsion des prismes", Mémoires des Savants Etrangers 14, 233-560 (1853) [in French].