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@article{AM2_1976__14_136619, author = {Ilie Corovei}, title = {The cosine functional equation for nilpotent groups. {(Short} {Communication).}}, journal = {Aequationes mathematicae}, pages = {511--511}, publisher = {mathdoc}, volume = {14}, year = {1976}, zbl = {0348.39004}, url = {http://geodesic.mathdoc.fr/item/AM2_1976__14_136619/} }
Ilie Corovei. The cosine functional equation for nilpotent groups. (Short Communication).. Aequationes mathematicae, Tome 14 (1976), p. 511. http://geodesic.mathdoc.fr/item/AM2_1976__14_136619/