Generation of two-dimensional digital functions without nonessential singularities of the second kind

A class of two-variable Hurwitz polynomials called very strict Hurwitz polynomials (VSHP's) is defined and its properties are studied. Their application in the generation of two-variable functions without nonessential singularities of the second kind is indicated. Necessary and sufficient conditions on general and reactance one-variable to two-variable transformations so that they yield two-variable transfer functions without singularities of the second kind are obtained.