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