@article{AL_1999_38_5_a0,
     author = {Ch. K. Gupta and E. I. Timoshenko},
     title = {Primitive systems of elements in the varieties $A_mA_n$: a},
     journal = {Algebra i logika},
     pages = {513--530},
     year = {1999},
     volume = {38},
     number = {5},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1999_38_5_a0/}
}