FOM: Question: Normal form

[G Barmpalias]

 A question:
 
 It has been obtained an improvement of the Normal for theorem for partial 
recursive functions, such that the (universal) predicate T_n and the function U 
belong to the smalest Grzegorczyk class E^0 (for every partial recursive 
function f, there an index e such that f(x)= U(\mu~y[T_n(e,x,y)]) ).
 
 Does any member of the list know a specific reference for this result?
 
 PS Odifreddi mentions the result in his book classical recursive functions 
Vol.II page 306.