@article{SM_2018_209_6_a4,
     author = {Ant. A. Klyachko and A. M. Mazhuga},
     title = {Verbally closed virtually free subgroups},
     journal = {Sbornik. Mathematics},
     pages = {850--856},
     publisher = {mathdoc},
     volume = {209},
     number = {6},
     year = {2018},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_2018_209_6_a4/}
}