@article{AL_1969_8_2_a6,
     author = {A. A. Urman},
     title = {Groupoid of varieties of certain algebras},
     journal = {Algebra i logika},
     pages = {241--250},
     publisher = {mathdoc},
     volume = {8},
     number = {2},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1969_8_2_a6/}
}