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