In Jech Set Theory, Theorem 19.3 (page 340 6'th line from the top) he claims that each premice is an initial segment for $<_{L[D]}$

OK, so the proof relies on existence of this sentence sigma_1 from 3.3(b) (then by elementarity every submodel of L[U] belongs to the hierarchy). Now - where can I find this sentence (Without using as a parameter L[U]) ? does this follow from the well ordering of L[U]?

Dear Andres, By L[U] I mean a k-model (k measurable) as is defined in Kanamori's section 20. I do refer to the "the non-fine structural version". The fine-structure version is indeed available in few places (best is Devlin) but I would like to know if there is a simpler one, without going into the morass of the J_alphas. Something along the lines of the L-version?