@article{1093894297, author = {Schumm, G. F.}, title = {Solutions to four modal problems of Soboci\'nski.}, journal = {Notre Dame J. Formal Logic}, volume = {12}, number = {1}, year = {1971}, pages = { 335-340}, language = {en}, url = {http://dml.mathdoc.fr/item/1093894297} }
Schumm, G. F. Solutions to four modal problems of Sobociński.. Notre Dame J. Formal Logic, Tome 12 (1971) no. 1, pp. 335-340. http://gdmltest.u-ga.fr/item/1093894297/