Comments on "Stability criterion for N-dimensional digital filters

In the above mentioned paper, a stability theorem is given for
n
-dimensional recursive filters. We show that for a certain class of filters, the theorem is open to misinterpretation, and consequently has frequently been applied incorrectly in the literature. Since the theorem has found greatest application in the context of two-dimensional (2-D) filtering, the 2-D case is examined in detail.