1. Functional Analysis [in Russian], "Nauka," Moscow (1964).
2. S. G. Krein, "Oscillations of a viscous liquid in a vessel," Dokl. Akad. Nauk SSSR,159, No. 2, 262?265 (1964).
3. G. I. Laptev, Boundary-Value Problems for Second-Order Differential Equations in Banach Space and Their Applications [in Russian], Dissertation, Voronezh University (1964).
4. I. Ts. Gokhberg and M. G. Krein, Introduction to the Theory of Nonselfadjoint Operators [in Russian], "Nauka," Moscow (1965).
5. J. Gobert, "Une inégalité fondamentale de la théorie de l'élasticité," Bull. Soc. Roy. Sci. Liége, No. 3?4, 182?191 (1962).