@article{AL_1996_35_3_a4,
     author = {I. V. Latkin},
     title = {Arithmetic hierarchy of torsion-free nilpotent groups},
     journal = {Algebra i logika},
     pages = {308--313},
     publisher = {mathdoc},
     volume = {35},
     number = {3},
     year = {1996},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1996_35_3_a4/}
}