@article{10_21136_CMJ_1961_100459,
     author = {Frol{\'\i}k, Zden\v{e}k},
     title = {Invariance of $G_\delta$-spaces under mappings},
     journal = {Czechoslovak Mathematical Journal},
     pages = {258--261},
     publisher = {mathdoc},
     volume = {11},
     number = {2},
     year = {1961},
     doi = {10.21136/CMJ.1961.100459},
     mrnumber = {0126251},
     zbl = {0151.29605},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1961.100459/}
}