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