books.google.co.uk - ..."The book, written by one of the main researchers on the field, gives a complete account of the theory of r.e. degrees. .... The definitions, results and proofs are always clearly motivated and explained before the formal presentation; the proofs are described with remarkable clarity and conciseness....http://books.google.co.uk/books/about/Recursively_Enumerable_Sets_and_Degrees.html?id=9I7Pl00LU5gC&q=Theorem+3.1&utm_source=gb-gplus-shareRecursively Enumerable Sets and Degrees
