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@article{CM_1938__5__357_0, author = {Turing, A. M.}, title = {The extensions of a group}, journal = {Compositio Mathematica}, pages = {357--367}, publisher = {Johnson Reprint Corporation}, volume = {5}, year = {1938}, zbl = {0018.39201}, language = {en}, url = {http://geodesic.mathdoc.fr/item/CM_1938__5__357_0/} }
Turing, A. M. The extensions of a group. Compositio Mathematica, Tome 5 (1938), pp. 357-367. http://geodesic.mathdoc.fr/item/CM_1938__5__357_0/