Voir la notice de l'article provenant de la source Math-Net.Ru
@article{DAN_1972_205_5_a1, author = {M. S. Burgin}, title = {Central extensions in $\gamma$-categories}, journal = {Doklady Akademii Nauk}, pages = {1019--1021}, publisher = {mathdoc}, volume = {205}, number = {5}, year = {1972}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DAN_1972_205_5_a1/} }
M. S. Burgin. Central extensions in $\gamma$-categories. Doklady Akademii Nauk, Tome 205 (1972) no. 5, pp. 1019-1021. http://geodesic.mathdoc.fr/item/DAN_1972_205_5_a1/