{TAIL ~ The reflectors} comprise {HEAD ~ ruled surfaces} and are arranged to converge from entrance to exit apertures 
{ TAIL ~ The reflectors } comprise { HEAD ~ ruled surfaces } and are arranged to converge from entrance to exit apertures
TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH