Voir la notice de l'article provenant de la source Math-Net.Ru
@article{AL_1977_16_1_a6, author = {N. S. Romanovskii}, title = {Free subgroups of finitely-presented groups}, journal = {Algebra i logika}, pages = {88--97}, publisher = {mathdoc}, volume = {16}, number = {1}, year = {1977}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/AL_1977_16_1_a6/} }
N. S. Romanovskii. Free subgroups of finitely-presented groups. Algebra i logika, Tome 16 (1977) no. 1, pp. 88-97. http://geodesic.mathdoc.fr/item/AL_1977_16_1_a6/