In preferred embodiments, {HEAD ~ each} of x and y, independently, is {TAIL ~ an integer} between about 2 and 6 
is
In preferred embodiments , { HEAD ~ each } of x and y , independently , is { TAIL ~ an integer } between about 2 and 6
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH