Upon receiving requests from {HEAD ~ the combination} of {TAIL ~ requesters}, the corresponding priority vector is referred to and the next requester identifier on this list is selected 
of
Upon receiving requests from { HEAD ~ the combination } of { TAIL ~ requesters } , the corresponding priority vector is referred to and the next requester identifier on this list is selected
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH