@article{10_14712_1213_7243_2015_279,
     author = {Greb{\'\i}k, Jan},
     title = {Ultrafilter extensions of asymptotic density},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {25--37},
     publisher = {mathdoc},
     volume = {60},
     number = {1},
     year = {2019},
     doi = {10.14712/1213-7243.2015.279},
     mrnumber = {3946662},
     zbl = {07088823},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.14712/1213-7243.2015.279/}
}