@article{1183738452, author = {Perlis, Donald}, title = {An Extension of Ackermann's Set Theory}, journal = {J. Symbolic Logic}, volume = {37}, number = {1}, year = {1972}, pages = { 703-704}, language = {en}, url = {http://dml.mathdoc.fr/item/1183738452} }
Perlis, Donald. An Extension of Ackermann's Set Theory. J. Symbolic Logic, Tome 37 (1972) no. 1, pp. 703-704. http://gdmltest.u-ga.fr/item/1183738452/