1. Best approximation properties of spline functions of odd degree;de Boor;J. of Math. and Mech.,1963
2. Smoothest curve approximation;Holladay;Math. Tables and other Aids to Comput.,1957
3. Best interpolation formulas;Meyers;J. of Math. and Phys.,1950
4. Best approximate integration formulas; best approximation formulas;Sard;Amer. J. of Math.,1949
5. Linear Approximations, Math. Surveys No. 9;Sard,1963