1. A survey of results on the d-c.e. and n-c.e. degrees;Arslanov,2017
2. Recursive labeling systems and stability of recursive structures in hyperarithmetical degrees;Ash;Trans. Am. Math. Soc.,1986
3. Computable Structures and the Hyperarithmetical Hierarchy;Ash,2000
4. Degrees of unsolvability;Cooper,1971
5. Hierarchies of sets and degrees below 0′;Epstein,1981