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@article{MAT_1966_10_4_a1, author = {I. Berstein}, title = {On co-groups in the category of graded algebras}, journal = {Matematika}, pages = {32--44}, publisher = {mathdoc}, volume = {10}, number = {4}, year = {1966}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/MAT_1966_10_4_a1/} }
I. Berstein. On co-groups in the category of graded algebras. Matematika, Tome 10 (1966) no. 4, pp. 32-44. http://geodesic.mathdoc.fr/item/MAT_1966_10_4_a1/