1. A Note on Nonlinear Approximation Theory;Cheney,1968
2. Best Approximation in Strictly Convex Spaces;Spiess,1969
3. Approximation from a curve of functions;Hobby;Arch. Rational Mech. Anal.,1967
4. Variational Methods for the Study of Nonlinear Operators;Vainberg,1964
5. Functional Analysis in Normed Linear Spaces;Kantorovich,1964