1. Degrees of unsolvability complementary between r.e. degrees;Cooper;Ann. Math. Logic,1972
2. Minimal degrees of unsolvability and the full approximation construction;Epstein;Mem. Am. Math. Soc.,1975
3. Degrees of Unsolvability: Structure and Theory;Epstein,1979
4. Initial segments of the degrees below 0′;Epstein;Mem. Am. Math. Soc.,1981
5. Lower bounds for pairs of r.e. degrees;Lachlan,1966