@article{1093894303,
author = {Soboci\'nski, Boles\l aw},
title = {A proper subsystem of ${\rm S}4.{\rm O}4.$.},
journal = {Notre Dame J. Formal Logic},
volume = {12},
number = {1},
year = {1971},
pages = { 381-384},
language = {en},
url = {http://dml.mathdoc.fr/item/1093894303}
}
Sobociński, Bolesław. A proper subsystem of ${\rm S}4.{\rm O}4.$.. Notre Dame J. Formal Logic, Tome 12 (1971) no. 1, pp. 381-384. http://gdmltest.u-ga.fr/item/1093894303/