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@article{IVM_1982_11_a11, author = {T. A. Martynova}, title = {A groupoid of varieties of semigroups with zero}, journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika}, pages = {77--79}, publisher = {mathdoc}, number = {11}, year = {1982}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/IVM_1982_11_a11/} }
T. A. Martynova. A groupoid of varieties of semigroups with zero. Izvestiâ vysših učebnyh zavedenij. Matematika, no. 11 (1982), pp. 77-79. http://geodesic.mathdoc.fr/item/IVM_1982_11_a11/