@article{DAN_1973_212_5_a13,
     author = {S. A. Chunikhin},
     title = {On the definition of $\pi$-solvable and $\pi$-separable groups},
     journal = {Doklady Akademii Nauk},
     pages = {1078--1081},
     publisher = {mathdoc},
     volume = {212},
     number = {5},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1973_212_5_a13/}
}