Process 2000 begins with operation 2002, where the reader retrieves at least a TPK and {HEAD ~ an ES} from {TAIL ~ a tag} 
from
Process 2000 begins with operation 2002 , where the reader retrieves at least a TPK and { HEAD ~ an ES } from { TAIL ~ a tag }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL