@article{CMUC_1966_7_3_a8,
     author = {Havel, V\'aclav},
     title = {Join systems and closure spaces},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {335--341},
     year = {1966},
     volume = {7},
     number = {3},
     mrnumber = {0212650},
     zbl = {0146.16105},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1966_7_3_a8/}
}