@article{PORMA_1965__24_4_114968,
     author = {Costa, Newton C.A. da and Guillaume, Marcel},
     title = {N\'egations compos\'ees et loi de {Peirce} dans les syst\`emes $C_n$},
     journal = {Portugaliae mathematica},
     pages = {201--210},
     publisher = {mathdoc},
     volume = {24},
     number = {4},
     year = {1965},
     mrnumber = {0216937},
     zbl = {0192.02903},
     language = {fr},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1965__24_4_114968/}
}