Best Approximation Properties of Spline Functions of Odd Degree Carl de Boor Indiana University Mathematics Journal 1963 text pdf 10.1512/iumj.1963.12.12051 10.1512/iumj.1963.12.12051 en Indiana Univ. Math. J. 12 (1963) 747 - 749 state-of-the-art mathematics http://iumj.org/access/