@article{DM_2012_24_4_a1,
     author = {S. S. Marchenkov},
     title = {Definition of positively closed classes by endomorphism semigroups},
     journal = {Diskretnaya Matematika},
     pages = {19--26},
     publisher = {mathdoc},
     volume = {24},
     number = {4},
     year = {2012},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DM_2012_24_4_a1/}
}