@article{AL_2015_54_4_a8,
     author = {I. Sh. Kalimullin and M. Kh. Faizrakhmanov},
     title = {A hierarchy of classes of families and $n$-low degrees},
     journal = {Algebra i logika},
     pages = {536--541},
     publisher = {mathdoc},
     volume = {54},
     number = {4},
     year = {2015},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_2015_54_4_a8/}
}