@article{1093890724, author = {Satre, Thomas W.}, title = {Natural deduction rules for $S1^0-S4^0$.}, journal = {Notre Dame J. Formal Logic}, volume = {13}, number = {3}, year = {1972}, pages = { 565-568}, language = {en}, url = {http://dml.mathdoc.fr/item/1093890724} }
Satre, Thomas W. Natural deduction rules for $S1^0-S4^0$.. Notre Dame J. Formal Logic, Tome 13 (1972) no. 3, pp. 565-568. http://gdmltest.u-ga.fr/item/1093890724/