@article{DAN_1978_243_4_a7,
     author = {G. S. Makanin},
     title = {Recognizing the rank of coefficientless equations in a free semigroup},
     journal = {Doklady Akademii Nauk},
     pages = {851--854},
     year = {1978},
     volume = {243},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1978_243_4_a7/}
}