The poweroid, an extension of the mathematical notion of power

A. C. Aitken: On a generalization of formulae for polynomial interpolation Journal of the Institute of Actuaries, Vol. LXI (1930), p. 107. See also Proceedings of the Edinburgh Mathematical Society, Series 2, Vol. I (1929), p. 199. J. F. Steffensen: Interpolation (Baltimore 1927), § 2 and § 18, or the same articles in the Danish edition of 1925. N. E. Nörlund: Leçons sur les séries d’interpolation, Paris 1926.