Design of 2-D recursive digital filters with specified magnitude and constant group-delay responses by spectral factorization. - N. Nagamuthu; Maher A. Sid-Ahmed; Malayappan Shridhar (ICASSP, 1982)

Scaled and Scaling-Free McClellan Transformations for the Design of 2-d Digital filters. - N. Nagamuthu; M. N. S. Swamy (J. Circuits Syst. Comput., 1991)