@article{1183386508, author = {Beth, Evert}, title = {Review: Olaf Helmer, Languages with Expressions of Infinite Length}, journal = {J. Symbolic Logic}, volume = {4}, number = {1}, year = {1939}, language = {en}, url = {http://dml.mathdoc.fr/item/1183386508} }
Beth, Evert. Review: Olaf Helmer, Languages with Expressions of Infinite Length. J. Symbolic Logic, Tome 4 (1939) no. 1, . http://gdmltest.u-ga.fr/item/1183386508/