1. Smoothest curve approximation;Holladay;Math-Tables Aids Comput.,1957
2. Best approximation properties of the spline fit;Walsh;J. Math. Mech,1962
3. Best approximation properties of spline functions of odd degree;deBoor;J. Math. Mech.,1963
4. Spline interpolations and highest derivatives;Schoenberg,1964
5. Spline interpolations and best quadrative formulae;Schoenberg;Bull. Am. Math. Soc.,1964