@article{RM_2012_67_4_a2,
     author = {V. B. Shehtman},
     title = {Squares of modal logics with additional connectives},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {721--777},
     publisher = {mathdoc},
     volume = {67},
     number = {4},
     year = {2012},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/RM_2012_67_4_a2/}
}