On the functional equation f ( x ) + ∑ i = 1 n g i ( y i ) = h ( T ( x , y 1 , y 2 , . . . , y n ) ) C. T. Ng — 1973 Annales Polonici Mathematici
A functional equation and its application to information theory P. Kannappan; C. T. Ng — 1974 Annales Polonici Mathematici