@article{PORMA_1967__26_1_115001,
     author = {Nadler, Sam B. jr.},
     title = {Coverings by closed sets},
     journal = {Portugaliae mathematica},
     pages = {51--61},
     publisher = {mathdoc},
     volume = {26},
     number = {1},
     year = {1967},
     mrnumber = {0248747},
     zbl = {0186.56103},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1967__26_1_115001/}
}