@article{CMUC_1975__16_4_a2,
     author = {Sochor, Anton{\'\i}n},
     title = {Real classes in the ultrapower of hereditarily finite sets},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {637--640},
     publisher = {mathdoc},
     volume = {16},
     number = {4},
     year = {1975},
     mrnumber = {0389588},
     zbl = {0327.02047},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1975__16_4_a2/}
}