@article{1093957979, author = {Prior, A. N.}, title = {${\rm K}1,\,{\rm K}2$ and related modal systems.}, journal = {Notre Dame J. Formal Logic}, volume = {5}, number = {1}, year = {1964}, pages = { 299-304}, language = {en}, url = {http://dml.mathdoc.fr/item/1093957979} }
Prior, A. N. ${\rm K}1,\,{\rm K}2$ and related modal systems.. Notre Dame J. Formal Logic, Tome 5 (1964) no. 1, pp. 299-304. http://gdmltest.u-ga.fr/item/1093957979/