@article{AMLG_1978__19_137950,
     author = {Robert A. Di Paola},
     title = {The operator gap theorem in ...-recursion theory.},
     journal = {Archiv f\"ur mathematische Logik und Grundlagenforschung},
     pages = {115--130},
     publisher = {mathdoc},
     volume = {19},
     year = {1978},
     zbl = {0412.03031},
     url = {http://geodesic.mathdoc.fr/item/AMLG_1978__19_137950/}
}