Elementary theories and structural properties of d-c.e. and n-c.e. degrees
M. M. Arslanov, ISKANDER SH. KALIMULLIN, Mars M. Yamaleev · Lobachevskii Journal of Mathematics · 2016
This paper is a survey on the upper semilattices of Turing and enumeration degrees of n -c.e. sets. Questions on the structural properties of these semilattices, and some model-theoretic properties are considered.