@article{CMUC_1973__14_2_a13,
     author = {Frol{\'\i}k, Zden\v{e}k},
     title = {Hyper-extensions of $\sigma$-algebras},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {361--375},
     publisher = {mathdoc},
     volume = {14},
     number = {2},
     year = {1973},
     mrnumber = {0346115},
     zbl = {0276.28004},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1973__14_2_a13/}
}