A theorem concerning the composition of functions of several variables ranging over a finite set
Arto K. Salomaa · Journal of Symbolic Logic · 1960
Consider functions whose variables, finite in number, range over a fixed finite set N and whose values are elements of N. The elements of N are denoted simply by the natural numbers 1,2, …, n. There are nnm distinct m-place functions. If N is chosen to be the set of n truth-values then the functions considered are obviously truth-functions in n-valued logic.