@article{ZNSL_1972_32_a3,
     author = {N. K. Kossovski},
     title = {Some properties of solutions of equations in a~free semigroup},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {21--28},
     publisher = {mathdoc},
     volume = {32},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1972_32_a3/}
}