@article{MZM_1989_46_4_a4,
     author = {N. Ya. Medvedev},
     title = {Relative convexity of subgroups of finite rank},
     journal = {Matemati\v{c}eskie zametki},
     pages = {34--37},
     publisher = {mathdoc},
     volume = {46},
     number = {4},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1989_46_4_a4/}
}