@article{AL_1970_9_3_a0,
     author = {A. P. Biryukov},
     title = {Varieties of idempotent semigroups},
     journal = {Algebra i logika},
     pages = {255--273},
     publisher = {mathdoc},
     volume = {9},
     number = {3},
     year = {1970},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1970_9_3_a0/}
}