When {HEAD ~ an abnormal operation} occurs in the production line, it is thus easy to find which {TAIL ~ working group} is in trouble 
When { HEAD ~ an abnormal operation } occurs in the production line , it is thus easy to find which { TAIL ~ working group } is in trouble
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH