@article{AMLG_1960__5_137752,
     author = {G. Kreisel and J. Shoenfield},
     title = {Number theoretic concepts and recursive well-orderings.},
     journal = {Archiv f\"ur mathematische Logik und Grundlagenforschung},
     pages = {42--64},
     publisher = {mathdoc},
     volume = {5},
     year = {1960},
     zbl = {0129.00402},
     url = {http://geodesic.mathdoc.fr/item/AMLG_1960__5_137752/}
}