The belts tend to center themselves toward the high points of the crowns, but are narrow enough to leave edges of {HEAD ~ transported envelopes} free for {TAIL ~ registration} 
free for
The belts tend to center themselves toward the high points of the crowns , but are narrow enough to leave edges of { HEAD ~ transported envelopes } free for { TAIL ~ registration }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL