@article{CMUC_1990_31_1_a16,
     author = {Schwarz, Friedhelm},
     title = {Extensionable topological hulls and topological universe hulls inside the category of pseudotopological spaces},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {123--127},
     year = {1990},
     volume = {31},
     number = {1},
     mrnumber = {1056179},
     zbl = {0697.54008},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1990_31_1_a16/}
}