On trigonometric functional equations of rectangular type. P.K. Sahoo; J. Chung; P. Kannappan — 1997 Aequationes mathematicae
Characterizations of sum form information measures on open domains. B.R. Ebanks; P.K. Sahoo; P. Kannappan — 1997 Aequationes mathematicae
An application of a functional equation to information theory P. Kannappan; P. N. Rathie — 1972 Annales Polonici Mathematici
A functional equation and its application to information theory P. Kannappan; C. T. Ng — 1974 Annales Polonici Mathematici