@article{PDM_2016_4_a3,
     author = {D. V. Solomatin},
     title = {The ranks of planarity for~varieties~of~commutative~semigroups},
     journal = {Prikladna\^a diskretna\^a matematika},
     pages = {50--64},
     year = {2016},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/PDM_2016_4_a3/}
}