This work considers a special case of a 4-term, inhomogeneous, two-dimensional, linear partial difference equation with constant coefficients. The authors are apparently unaware of the published work on multi-term, homogeneous and inhomogeneous, $n$-dimensional, linear partial difference equations with non-constant and constant coefficients, also extended to include a system of a number of such equations which are linearly coupled. The conditions of existence of solutions have been previously determined and the solutions obtained in terms of combinatorial functions. Thus, all the results published in this article seem only special cases of the general formulation. See, for instance, the reviewer's papers on this subject.