1. Alber Y. Metric and generalized projection operators in Banach spaces: properties and applications. In: Kartsatos A, editor. Theory and applications of nonlinear operators of accretive and monotone type. Marcel Dekker, Inc.; 1996. p. 15–50.
2. James orthogonality and orthogonal decompositions of Banach spaces
3. Convex Analysis and Monotone Operator Theory in Hilbert Spaces
4. Questions on smallest quantities connected with the approximate representation of functions (1859);Chebyshev PL.;Collect Works,1947
5. Dunford N, Schwartz JT. Linear operators. I: general theory, pure and applied mathematics. Vol. 7. New York: Interscience; 1958.