@article{AL_1966_5_5_a1,
     author = {Yu. Sh. Gurevich},
     title = {The problem of equality of words for certain classes of},
     journal = {Algebra i logika},
     pages = {25--35},
     publisher = {mathdoc},
     volume = {5},
     number = {5},
     year = {1966},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1966_5_5_a1/}
}