I. M. Sheffer, “Some Properties of Polynomial Sets of Type Zero,” Duke Mathematical Journal, Vol. 5, No. 3, 1939, pp. 590-622. doi:10.1215/S0012-7094-39-00549-1
has been cited by the following article:
TITLE: Generalized Powers of Substitution with Pre-Function Operators
AUTHORS: Laurent Poinsot
KEYWORDS: Formal Power Series; Formal Substitution; Riordan Group; Generalized Powers; Sheffer Sequences; Umbral Calculus
JOURNAL NAME: Applied Mathematics, Vol.4 No.7A, July 5, 2013
ABSTRACT: An operator on formal power series of the form S μS , where μ is an invertible power series, and σ is a series of the formt+（t2）is called a unipotent substitution with pre-function. Such operators, denoted by a pair (μ ，σ ） , form a group. The objective of this contribution is to show that it is possible to define a generalized powers for such operators, as for instance fractional powers σ for every .