@article{MZM_1978_23_5_a12,
     author = {V. B. Shekhtman},
     title = {Two-dimensional modal logic},
     journal = {Matemati\v{c}eskie zametki},
     pages = {759--772},
     publisher = {mathdoc},
     volume = {23},
     number = {5},
     year = {1978},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1978_23_5_a12/}
}