{HEAD ~ Pending specifications} are {TAIL ~ specifications} that will not execute until some condition or conditions are satisfied on the client 
{ HEAD ~ Pending specifications } are { TAIL ~ specifications } that will not execute until some condition or conditions are satisfied on the client
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH