@article{CMUC_1971__12_3_a4,
     author = {Je\v{z}ek, Jaroslav},
     title = {The existence of upper semicomplements in lattices of primitive classes},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {519--532},
     publisher = {mathdoc},
     volume = {12},
     number = {3},
     year = {1971},
     mrnumber = {0292734},
     zbl = {0225.08006},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1971__12_3_a4/}
}