@article{CMUC_1970__11_2_a10,
     author = {Pechanec, Jaroslav},
     title = {Modifications of closure collections},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {379--384},
     publisher = {mathdoc},
     volume = {11},
     number = {2},
     year = {1970},
     mrnumber = {0266202},
     zbl = {0197.18801},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1970__11_2_a10/}
}