@article{AMLG_1960__5_137751,
     author = {A. Ehrenfeucht and S. Feferman},
     title = {Representability of recursively enumerable sets in formal theories.},
     journal = {Archiv f\"ur mathematische Logik und Grundlagenforschung},
     pages = {37--41},
     publisher = {mathdoc},
     volume = {5},
     year = {1960},
     zbl = {0118.25102},
     url = {http://geodesic.mathdoc.fr/item/AMLG_1960__5_137751/}
}