The protect string specifies {HEAD ~ the authentication scheme} or schemes that need to be implemented for {TAIL ~ that request} 
implemented for
The protect string specifies { HEAD ~ the authentication scheme } or schemes that need to be implemented for { TAIL ~ that request }
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL