@article{AL_1977_16_2_a6,
     author = {I. P. Shestakov},
     title = {A problem of {\v{S}ir\v{s}ov}},
     journal = {Algebra i logika},
     pages = {227--246},
     publisher = {mathdoc},
     volume = {16},
     number = {2},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1977_16_2_a6/}
}