The elements of are the set of {TAIL ~ exponents} dk+1, i.e. exponents of {HEAD ~ σ} 
The elements of are the set of { TAIL ~ exponents } dk+1 , i.e. exponents of { HEAD ~ σ }
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD