@article{PORMA_1949__8_4_114681,
     author = {Gi\~ao, Ant\'onio},
     title = {On the origin of positive and negative electricity},
     journal = {Portugaliae mathematica},
     pages = {143--153},
     publisher = {mathdoc},
     volume = {8},
     number = {4},
     year = {1949},
     mrnumber = {0044946},
     zbl = {0040.27901},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1949__8_4_114681/}
}