at least one of {TAIL ~ said first and second reflectors} is inclined to have {HEAD ~ a non zero reflection angle} 
at least one of { TAIL ~ said first and second reflectors } is inclined to have { HEAD ~ a non zero reflection angle }
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD