1. C.T. Chong, Relativized incomparable α-r.e. degrees and non-branching α-r.e. degrees, J. Symbolic Logic, to appear.
2. Three theorems on recursive enumeration;Friedberg;J. Symbolic Logic,1958
3. The fine structure of the constructible hierarchy;Jensen;Ann. Math. Logic,1972
4. On the lattice of recursively enumerable sets;Lachlan;Trans. Am. Math. Soc.,1968
5. Maximal α-r.e. sets and their complements;Leggett,1973