@article{1183736451, author = {Feferman, Solomon}, title = {Review: Azriel Levy, A Hierarchy of Formulas in Set Theory}, journal = {J. Symbolic Logic}, volume = {33}, number = {1}, year = {1968}, pages = { 473-474}, language = {en}, url = {http://dml.mathdoc.fr/item/1183736451} }
Feferman, Solomon. Review: Azriel Levy, A Hierarchy of Formulas in Set Theory. J. Symbolic Logic, Tome 33 (1968) no. 1, pp. 473-474. http://gdmltest.u-ga.fr/item/1183736451/