A hierarchy of Turing degrees a transfinite hierarchy of lowness notions in the computably enumerable degrees, unifying classes, and natural definability von Downey, R. G. (Rod G.), Greenberg, Noam 1974-

Also available remotely for University of the Philippines System via IEEE Xplore. Click here to access thru EZproxy
Available for University of the Philippines System via IEEE Xplore. Click here to access