@article{CMUC_1969__10_4_a5,
     author = {\v{C}ih\'ak, Pavel},
     title = {A combinatorial theorem on the existence of a separating element and its applications to sequences and $\sigma$-derivations of measures},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {593--611},
     publisher = {mathdoc},
     volume = {10},
     number = {4},
     year = {1969},
     mrnumber = {0262448},
     zbl = {0208.07005},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1969__10_4_a5/}
}