{HEAD ~ Tp} is typically {TAIL ~ between 20 and 300 seconds} and αt between 0 and 5 
is typically
{ HEAD ~ Tp } is typically { TAIL ~ between 20 and 300 seconds } and αt between 0 and 5
HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH