Another advantage is that tracking records do not have to be explicitly created in {HEAD ~ a tracking operation} for {TAIL ~ marked items} contained in another marked item 
for
Another advantage is that tracking records do not have to be explicitly created in { HEAD ~ a tracking operation } for { TAIL ~ marked items } contained in another marked item
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH