@article{AM2_1973__9_136337,
     author = {A.N. SARKOVSKII},
     title = {Characterization of the {Cosine} {(Russisch)}},
     journal = {Aequationes mathematicae},
     pages = {121--128},
     publisher = {mathdoc},
     volume = {9},
     year = {1973},
     url = {http://geodesic.mathdoc.fr/item/AM2_1973__9_136337/}
}