@article{10_21136_CMJ_1972_101078,
     author = {Bican, Ladislav},
     title = {Pure closures},
     journal = {Czechoslovak Mathematical Journal},
     pages = {78--82},
     publisher = {mathdoc},
     volume = {22},
     number = {1},
     year = {1972},
     doi = {10.21136/CMJ.1972.101078},
     mrnumber = {0294385},
     zbl = {0235.16026},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1972.101078/}
}