@article{IVM_1981_4_a7,
     author = {M. V. Sapir and E. V. Sukhanov},
     title = {Varieties of periodic semigroups},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {48--55},
     year = {1981},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1981_4_a7/}
}