1. K. Ambos-Spies, On the structure of the recursively enumerable degrees, Ph.D. dissertation, Univ. of Munich.
2. \bysame, An extension of the non-diamond theorem in classical and 𝛼-recursion theory, J. Symbolic Logic.
3. \bysame, Non-cappability in the r.e. weak truth table and Turing degrees,
4. P. Fejer, The structure of definable subclasses of the recursively enumerable degrees, Ph.D. dissertation, Univ. of Chicago.
5. The plus-cupping theorem for the recursively enumerable degrees;Fejer, Peter A.,1981