It is shown that for any 2-computably enumerable Turing degree l, any computably enumerable degree a, and any Turing degree s, if l = 0 , l < a, s 0 , and s is c.e. in a, then there is a 2-computably enumerable degree x with the following properties: (1) l < x < a, and (2) x = s.
Carl G. Jockusch Jr., Angsheng Li