@article{ZNSL_1995_220_a4,
     author = {N. K. Kossovski},
     title = {Level logics},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {72--82},
     year = {1995},
     volume = {220},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1995_220_a4/}
}