Stephen G. Simpson. Sets Which Do Not Have Subsets of Every Higher Degree. Journal of Symbolic Logic, 43(1):135-138, 1978.
@article{Simpson78,
title = {Sets Which Do Not Have Subsets of Every Higher Degree},
author = {Stephen G. Simpson},
year = {1978},
researchr = {https://researchr.org/publication/Simpson78},
cites = {0},
citedby = {0},
journal = {Journal of Symbolic Logic},
volume = {43},
number = {1},
pages = {135-138},
}