@book{1722980,
	author = {Downey},
	title = {A Hierarchy of Turing Degrees: A Transfinite Hierarchy of Lowness Notions in the Computably Enumerable Degrees, Unifying Classes, and Natural Definability (AMS-206)},
	publisher = {IEEE},
	url = {https://ieeexplore.ieee.org/servlet/opac?bknumber=9452519}
}