A first on disc position is related to {HEAD ~ an innermost position} within {TAIL ~ the second data recorded region} 
within
A first on disc position is related to { HEAD ~ an innermost position } within { TAIL ~ the second data recorded region }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL