On Normal Pointsystems of Hermite-Fejér Interpolation of Arbitrary Order

Necessary conditions of normal pointsystems for Hermite-Fejer interpolation of arbitrary (even) order are given. In particular, one of the main results in this paper is: If a pointsystem consists of the zeros of orthogonal polynomials with respect to a weight w on [-1, 1] and is always normal for Hermite-Fejer interpolation of arbitrary (even) order, then w(x)~(1-x^2)^-^1^/^2.