@article{MAN_1963__152_161100,
     author = {P. AXT},
     title = {Relativization of a primitive recursive hierarchy.},
     journal = {Mathematische Annalen},
     pages = {159--163},
     publisher = {mathdoc},
     volume = {152},
     year = {1963},
     zbl = {0118.25101},
     url = {http://geodesic.mathdoc.fr/item/MAN_1963__152_161100/}
}