@article{MZM_1968_4_6_a1,
     author = {V. M. Kotlov},
     title = {On varieties of $n$-solvable groups},
     journal = {Matemati\v{c}eskie zametki},
     pages = {629--634},
     publisher = {mathdoc},
     volume = {4},
     number = {6},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1968_4_6_a1/}
}