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