@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/