@article{10_4064_fm_49_3_295_300,
     author = {A. Lelek and Jan Mycielski},
     title = {Some conditions for a mapping to be a covering},
     journal = {Fundamenta Mathematicae},
     pages = {295--300},
     publisher = {mathdoc},
     volume = {49},
     number = {3},
     year = {1960},
     doi = {10.4064/fm-49-3-295-300},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm-49-3-295-300/}
}