@article{PIM_1982_N_S_32_46_a7,
     author = {Czeslaw Dyjak},
     title = {On {A} {Characterization} {Of} {Trigonometrical} {And} {Hyperbolic} {Functions} {By} {Functional} {Equations}},
     journal = {Publications de l'Institut Math\'ematique},
     pages = {45 },
     publisher = {mathdoc},
     volume = {_N_S_32},
     number = {46},
     year = {1982},
     url = {http://geodesic.mathdoc.fr/item/PIM_1982_N_S_32_46_a7/}
}