@article{1261147294, author = {M. SMULLYAN, Raymond}, title = {Elementary formal systems}, journal = {J. Math. Soc. Japan}, volume = {13}, number = {4}, year = {1961}, pages = { 38-44}, language = {en}, url = {http://dml.mathdoc.fr/item/1261147294} }
M. SMULLYAN, Raymond. Elementary formal systems. J. Math. Soc. Japan, Tome 13 (1961) no. 4, pp. 38-44. http://gdmltest.u-ga.fr/item/1261147294/