1. C.T. Chong, Maximal sets and fragments of Peano arithmetic, Nagoya Math. J., to appear.
2. C.T. Chong, Recursively enumerable sets in models of Σ2 collection, to appear.
3. Hyperhypersimple α r.e. sets;Chong;Ann. Math. Logic,1976
4. Three theorems on recursive enumeration: I. Decomposition, II. Maximal set,III. enumeration without duplication;Friedberg;J. Symbolic Logic,1957
5. M. Groszek and T.A. Slaman, On Turing reducibility, to appear.