Manuel Lerman. Upper bounds for the arithmetical degrees. Annals of Pure and Applied Logic, 29(3):225-254, 1985. [doi]
@article{Lerman85,
title = {Upper bounds for the arithmetical degrees},
author = {Manuel Lerman},
year = {1985},
doi = {10.1016/0168-0072(85)90001-6},
url = {http://dx.doi.org/10.1016/0168-0072(85)90001-6},
researchr = {https://researchr.org/publication/Lerman85},
cites = {0},
citedby = {0},
journal = {Annals of Pure and Applied Logic},
volume = {29},
number = {3},
pages = {225-254},
}