@article{1183741687, author = {Henson, C. Ward and Kaufmann, Matt and Keisler, H. Jerome}, title = {The Strength of Nonstandard Methods in Arithmetic}, journal = {J. Symbolic Logic}, volume = {49}, number = {1}, year = {1984}, pages = { 1039-1058}, language = {en}, url = {http://dml.mathdoc.fr/item/1183741687} }
Henson, C. Ward; Kaufmann, Matt; Keisler, H. Jerome. The Strength of Nonstandard Methods in Arithmetic. J. Symbolic Logic, Tome 49 (1984) no. 1, pp. 1039-1058. http://gdmltest.u-ga.fr/item/1183741687/