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