1. Local spline approximation by moments;Birkhoff;J. Math. Mech.,1967
2. Spline approximation by quasi-interpolants;de Boor;J. Approximation Theory,1973
3. Piecewise polynomial approximation on optimal meshes;Burchard;J. Approximation Theory,1975
4. Optimal order approximation by polynomial spline functions;Dodson,1972
5. On the degree of convergence of nonlinear spline approximation;Rice,1969