@article{DAN_1987_295_3_a3,
     author = {A. D. Korshunov},
     title = {On the power and structure of some closed {Post} classes (families},
     journal = {Doklady Akademii Nauk},
     pages = {533--537},
     publisher = {mathdoc},
     volume = {295},
     number = {3},
     year = {1987},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1987_295_3_a3/}
}