Carl G. JockuschJr., and David B. Posner. Double jumps of minimal degrees. The journal of symbolic logic, vol. 43 no. 4 (for 1978, pub. 1979), pp. 715–724. - Carl G. JockuschJr., and David B. Posner. Automorphism bases for degrees of unsotvability. Israel journal of mathematics, vol. 40 (1981), pp. 150–164. - Richard L. Epstein. Initial segments of degrees below 0′. Memoirs of the American Mathematical Society, no. 241. American Mathematical Society, Providence1981, vi + 102 pp. - Richard A. Shore. The theory of the degrees below 0′. The journal of the London Mathematical Society, ser. 2 vol. 24 (1981), pp. 1–14.
1985 ◽
Vol 50
(2)
◽
pp. 550-552