In an embodiment, region 38 has {HEAD ~ a depth} essentially equal to {TAIL ~ the depth} of region 34 
essentially equal to
In an embodiment , region 38 has { HEAD ~ a depth } essentially equal to { TAIL ~ the depth } of region 34
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH