ON REDUCIBILITIES OF NUMERATIONS
Aleksandr Nikolaevich Degtev · Mathematics of the USSR-Sbornik · 1981
If and are two numerations of the set , then will be said to be -reducible to provided there exists an enumeration operator such that () . In this paper both -reducibility and upper semilattices of -equivalent computable families of recursively enumerable sets are studied. Some of these semilattices admit an elegant description; for others sufficient conditions are found in order that they have an -principal numeration or be countable. Bibliography: 7 titles.