@article{AL_1970_9_4_a1,
     author = {A. D. Bol'bot},
     title = {Varieties of $\Omega $-algebras},
     journal = {Algebra i logika},
     pages = {406--414},
     publisher = {mathdoc},
     volume = {9},
     number = {4},
     year = {1970},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1970_9_4_a1/}
}