@article{1093635420, author = {Hawthorn, John}, title = {Natural deduction in normal modal logic.}, journal = {Notre Dame J. Formal Logic}, volume = {31}, number = {2}, year = {1990}, pages = { 263-273}, language = {en}, url = {http://dml.mathdoc.fr/item/1093635420} }
Hawthorn, John. Natural deduction in normal modal logic.. Notre Dame J. Formal Logic, Tome 31 (1990) no. 2, pp. 263-273. http://gdmltest.u-ga.fr/item/1093635420/