@article{AL_1984_23_5_a5,
     author = {V. V. Rybakov},
     title = {A criterion for admissibility of rules in the modal system},
     journal = {Algebra i logika},
     pages = {546--572},
     publisher = {mathdoc},
     volume = {23},
     number = {5},
     year = {1984},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1984_23_5_a5/}
}