selecting content for and distributing {HEAD ~ content} to {TAIL ~ users} based on their association with the affinity group 
to
selecting content for and distributing { HEAD ~ content } to { TAIL ~ users } based on their association with the affinity group
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH