{HEAD ~ Each trough shaped reflector} has {TAIL ~ an associated flat reflecting mirror} for directing its beam of illuminating light toward the document 
has
{ HEAD ~ Each trough shaped reflector } has { TAIL ~ an associated flat reflecting mirror } for directing its beam of illuminating light toward the document
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH