1. J. Schauder, Der Fixpunktsatz in Funktionalräumen, Studia Math., 2, 171?180 (1930).
2. M. A. Krasnosel'skii, Topological Methods in the Theory of Nonlinear Integral Equations [in Russian], Moscow, Gostekhizdat (1956).
3. M. A. Krasnosel'skii, Two notes on the method of successive approximations, Uspekhi Matematicheskikh Nauk,10, 123?127 (1955).
4. N. Dunford and J. Schwartz, Linear Operators [Russian translation], Moscow, IL (1962).