1. Effective coloration;Bean;J. Symbolic Logic,1976
2. Recursive Euler and Hamilton paths;Bean,1976
3. A decomposition theorem for partially ordered sets;Dilworth;Annals of Math.,1950
4. Countable retracing functions and Π20 predicates;Jockusch;Pacific J. Math.,1969
5. Π10 classes and degrees of theories;Joakusch;Trans. Amer. Math. Soc.,1972