@article{AL_1974_13_2_a5,
     author = {L. L. Maksimova and V. V. Rybakov},
     title = {The lattice of normal modal logics},
     journal = {Algebra i logika},
     pages = {188--216},
     publisher = {mathdoc},
     volume = {13},
     number = {2},
     year = {1974},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1974_13_2_a5/}
}