Clearly, we need at least one target element satisfying {HEAD ~ all} of Requirements R1, R2, and {TAIL ~ R3} for each payload bit to be embedded 
Clearly , we need at least one target element satisfying { HEAD ~ all } of Requirements R1 , R2 , and { TAIL ~ R3 } for each payload bit to be embedded
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH