@article{TRSPY_1971_107_a0,
     author = {Yu. I. Khmelevskii},
     title = {Equations in a free semigroup},
     journal = {Informatics and Automation},
     pages = {3--288},
     publisher = {mathdoc},
     volume = {107},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TRSPY_1971_107_a0/}
}