@article{MZM_1989_45_5_a3,
     author = {A. A. Kravchenko},
     title = {Balanced and cobalanced {Butler} groups},
     journal = {Matemati\v{c}eskie zametki},
     pages = {32--37},
     publisher = {mathdoc},
     volume = {45},
     number = {5},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1989_45_5_a3/}
}