@article{AL_1986_25_2_a4,
     author = {N. G. Khisamiev},
     title = {Hierarchies of torsion-free abelian groups},
     journal = {Algebra i logika},
     pages = {205--226},
     publisher = {mathdoc},
     volume = {25},
     number = {2},
     year = {1986},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1986_25_2_a4/}
}