@article{MZM_2015_97_5_a2,
     author = {D. V. Gol'tsov},
     title = {Approximability of {HNN-Extensions} with {Central} {Associated} {Subgroups} by a {Root} {Class} of {Groups}},
     journal = {Matemati\v{c}eskie zametki},
     pages = {665--669},
     publisher = {mathdoc},
     volume = {97},
     number = {5},
     year = {2015},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_2015_97_5_a2/}
}