I've searched the net,but no succes in finding a Pansops site,so ,next time on office I'll check some books..
My explanation is based also on our SOP,some thsd's hrs of line flying and also answer given to me by some ATC friends....
But,I'll check the books,and maybe I'll find a definite answer for you,page and paragraph....
I also want to find this,cause I'm surprised that there are pilots who apply drift correction when instructed to maintain HEADING ,thus not knowing or not making any difference between Heading and Track (check also definitions for these two notions..)