@article{PORMA_1949__8_2_114675,
     author = {Halld\'en, S.},
     title = {A reduction of the primitive symbols of the {Lewis} calculi},
     journal = {Portugaliae mathematica},
     pages = {85--88},
     publisher = {mathdoc},
     volume = {8},
     number = {2},
     year = {1949},
     mrnumber = {0038310},
     zbl = {0037.29501},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1949__8_2_114675/}
}