@article{10_21136_CMJ_1971_101057,
     author = {Pechanec-Draho\v{s}, Jaroslav},
     title = {Modifications of closure collections},
     journal = {Czechoslovak Mathematical Journal},
     pages = {577--589},
     year = {1971},
     volume = {21},
     number = {4},
     doi = {10.21136/CMJ.1971.101057},
     mrnumber = {0487957},
     zbl = {0225.54006},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1971.101057/}
}