@article{1183740337, author = {Benthem, J. F. A. K. Van}, title = {Canonical Modal Logics and Ultrafilter Extensions}, journal = {J. Symbolic Logic}, volume = {44}, number = {1}, year = {1979}, pages = { 1-8}, language = {en}, url = {http://dml.mathdoc.fr/item/1183740337} }
Benthem, J. F. A. K. Van. Canonical Modal Logics and Ultrafilter Extensions. J. Symbolic Logic, Tome 44 (1979) no. 1, pp. 1-8. http://gdmltest.u-ga.fr/item/1183740337/