@article{AM2_1974__11_136445,
     author = {L.B. Etigson},
     title = {A {Cosine} {Functional} {Equation} with {Restricted} {Argument.} {(Short} {Communication).}},
     journal = {Aequationes mathematicae},
     pages = {118--118},
     publisher = {mathdoc},
     volume = {11},
     year = {1974},
     zbl = {0318.39006},
     url = {http://geodesic.mathdoc.fr/item/AM2_1974__11_136445/}
}