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