Hi - this is my first post. I'm a recent PhD particle experimentalist; though I'm trying to get a better understanding of underlying theory in my spare time (I hope to contribute more here later). My question - does anyone know a good source for a derivation of the P_gg (gluon-gluon) splitting function in the Altarelli-Parisi/DGLAP evolution equations? This hasn't been an easy thing to come by. I've worked through solutions for P_qq, P_qg and P_gq ; P_gg is apparently considerably trickier, and explicit solutions seem accordingly more difficult to come by. I've looked at Altarelli, Parisi's original paper, and I'm having trouble with the notation; I'm wondering if there's a (newer?) textbook out there that works this out explicitly. Thanks!