1. Optimal approximations and error bounds;Golomb,1959
2. Lectures on Theory of Approximation;Golomb,1962
3. On interpolation by spline functions and its minimal properties;Schoenberg,1964
4. Vorlesungen ueber Differenzenrechnung;Nörlund,1924
5. Orthogonality properties of spline functions;Ahlberg;J. Math. Anal. Appl.,1965