@article{10_4064_ap_20_3_245_249,
     author = {Pl. Kannappan},
     title = {On cosine and sine functional equations},
     journal = {Annales Polonici Mathematici},
     pages = {245--249},
     publisher = {mathdoc},
     volume = {20},
     number = {3},
     year = {1968},
     doi = {10.4064/ap-20-3-245-249},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-20-3-245-249/}
}