@article{ZNSL_1986_154_a14,
     author = {V. A. Shlyk},
     title = {Generalized quadrangles, symmetrization and nonunivalent mappings},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {163--174},
     publisher = {mathdoc},
     volume = {154},
     year = {1986},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1986_154_a14/}
}