The ledger may be kept at a central control system, at {HEAD ~ a local network} for {TAIL ~ localized transaction tracking}, or at a remote network for more regional or national transaction tracking 
for
The ledger may be kept at a central control system , at { HEAD ~ a local network } for { TAIL ~ localized transaction tracking } , or at a remote network for more regional or national transaction tracking
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH