1. The Theory of Splines and Their Applications;Ahlberg,1967
2. Extremal, orthogonality and convergence properties of multi-dimensional splines;Ahlberg;J. Math. Anal. Appl.,1965
3. Piecewise polynomial interpolation and approximation;Birkhoff,1965
4. Smooth surface interpolation;Birkhoff;J. Math. Phys.,1960
5. Piecewise bicubic interpolation and approximation in polygons;Birkhoff,1969