1. Introduction to Approximation Theory;Cheney,1966
2. Interpolation and Approximation;Davis,1963
3. On the dimensionality of polytopes of best approximation for differentiable functions;Garkavi;Izv. Akad. Nauk. SSSR Ser. Mat.,1959
4. A characterization of Haar subspaces in C[a, b];Ikebe,1968
5. Unicity in approximation of a function and its derivatives;Johnson;Math. Comp.,1968