@article{SM_1983_44_1_a5,
     author = {Yu. M. Vazhenin and B. V. Rozenblat},
     title = {Decidability of the positive theory of a~free countably generated semigroup},
     journal = {Sbornik. Mathematics},
     pages = {109--116},
     year = {1983},
     volume = {44},
     number = {1},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1983_44_1_a5/}
}