Geodesic
Birkhoff Interpolation at the nth Roots of Unity: Convergence
Canadian journal of mathematics, Tome 33 (1981) no. 2, pp. 362-371

Voir la notice de l'article provenant de la source Cambridge University Press

The first investigations on this type of problem were carried out by O. Kiš [2]. Kiš considered the problem of interpolating a function and its second derivative at the nth roots of unity (the (0, 2) problem) by 2n – 1 degree polynomials, and the convergence of such approximates. Later, Sharma [8], [9] extended the existence and uniqueness results to (0, m) interpolation, and essentially to (0, m 1, m 2) interpolation. In the latter case, Sharma established the convergence results for (0, 2, 3), (0, 1, 3) and (0, 1, 4) interpolation as well. Although some further special cases were considered [10] these were the essential results until very recently. Now Cavaretta, Sharma and Varga [1] have established the existence and uniqueness theorem for all possible interpolations of this type (see Theorem 2.1 below). Motivated by the work of Cavaretta, Sharma and Varga and the earlier work of Sharma [9], a different proof of this result is provided, and this proof is used to establish a convergence theorem in the general case. 
Riemenschneider, S. D.; Sharma, A. Birkhoff Interpolation at the nth Roots of Unity: Convergence. Canadian journal of mathematics, Tome 33 (1981) no. 2, pp. 362-371. doi: 10.4153/CJM-1981-030-9
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