1. Splines (with Optimal Knots) Are Better;Burchard;J. Applicable Analysis,1974
2. Direct and converse theorems for piecewise polynomial approximation on optimal partitions, abstract;Burchard;Notices Amer. Math. Soc.,1973
3. Good approximation by splines with variable knots;de Boor,1972
4. Optimal order approximation by polynomial spline functions;Dodson,1972
5. Some questions connected with approximation by spline functions and polynomials (Russian);Freud;Studia Sci. Math. Hungar.,1970