@article{AL_1991_30_6_a2,
     author = {V. A. Lyubetskii},
     title = {The transition from deducibility in classical set theory to},
     journal = {Algebra i logika},
     pages = {652--670},
     publisher = {mathdoc},
     volume = {30},
     number = {6},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1991_30_6_a2/}
}