{HEAD ~ A period} of {TAIL ~ extended use}, as used in this application, means a period of use of more than about one hour, and generally more than four hours and less than twelve hours 
of
{ HEAD ~ A period } of { TAIL ~ extended use } , as used in this application , means a period of use of more than about one hour , and generally more than four hours and less than twelve hours
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH