Alternatively, the chewing gum may contain {HEAD ~ combinations} of {TAIL ~ sugar} and sugarless sweeteners 
of
Alternatively , the chewing gum may contain { HEAD ~ combinations } of { TAIL ~ sugar } and sugarless sweeteners
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH