{HEAD ~ A bounding web site} is characterized by the best data values from among {TAIL ~ all field web sites} 
{ HEAD ~ A bounding web site } is characterized by the best data values from among { TAIL ~ all field web sites }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL