@article{AM2_1997__53_1-2_137676, author = {P.K. Sahoo and J. Chung and P. Kannappan}, title = {On trigonometric functional equations of rectangular type.}, journal = {Aequationes mathematicae}, pages = {36--53}, publisher = {mathdoc}, volume = {53}, number = {1-2}, year = {1997}, zbl = {0901.39007}, url = {http://geodesic.mathdoc.fr/item/AM2_1997__53_1-2_137676/} }