In alternate embodiments, {HEAD ~ stacking arrangements} include: {TAIL ~ gamma structures} alone; or delta structures alone 
include
In alternate embodiments , { HEAD ~ stacking arrangements } include : { TAIL ~ gamma structures } alone ; or delta structures alone
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH