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