@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/