A sorting installation uses {TAIL ~ predetermined separating elements} which may be differentiated from {HEAD ~ the articles} 
A sorting installation uses { TAIL ~ predetermined separating elements } which may be differentiated from { HEAD ~ the articles }
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD