@article{AL_1972_11_6_a2,
     author = {S. D. Denisov},
     title = {Models of a noncontradictory formula and the hierarchy of {Er\v{s}ov}},
     journal = {Algebra i logika},
     pages = {648--655},
     publisher = {mathdoc},
     volume = {11},
     number = {6},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1972_11_6_a2/}
}