@article{2511, author = {Nadler, Sam B. jr.}, title = {Coverings by closed sets}, journal = {Portugaliae mathematica}, volume = {26}, year = {1967}, pages = {51-61}, zbl = {0186.56103}, mrnumber = {0248747}, language = {en}, url = {http://dml.mathdoc.fr/item/2511} }
Nadler, Sam B. jr. Coverings by closed sets. Portugaliae mathematica, Tome 26 (1967) pp. 51-61. http://gdmltest.u-ga.fr/item/2511/