@article{SM_1985_50_2_a4,
     author = {P. M. Beletskii},
     title = {Dense subclasses in some varieties of two-step nilpotent groups},
     journal = {Sbornik. Mathematics},
     pages = {369--385},
     publisher = {mathdoc},
     volume = {50},
     number = {2},
     year = {1985},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1985_50_2_a4/}
}