@article{1093890625, author = {Kielkopf, Charles F.}, title = {Kripke's axiomatization of ${\rm S2}$.}, journal = {Notre Dame J. Formal Logic}, volume = {13}, number = {3}, year = {1972}, pages = { 379-380}, language = {en}, url = {http://dml.mathdoc.fr/item/1093890625} }
Kielkopf, Charles F. Kripke's axiomatization of ${\rm S2}$.. Notre Dame J. Formal Logic, Tome 13 (1972) no. 3, pp. 379-380. http://gdmltest.u-ga.fr/item/1093890625/