@article{AM2_1986__31_137139,
     author = {H.L. Vasudeva and J.C. Parnami},
     title = {A comparative study of functional equations characterising sine and cosine.},
     journal = {Aequationes mathematicae},
     pages = {26--33},
     publisher = {mathdoc},
     volume = {31},
     year = {1986},
     zbl = {0607.39004},
     url = {http://geodesic.mathdoc.fr/item/AM2_1986__31_137139/}
}