A SIM server provides access to the SIMs, a SIM librarian catalogs the SIMs, and a SIM accounting system tracks {HEAD ~ and/bills} for {TAIL ~ SIM usage} 
A SIM server provides access to the SIMs , a SIM librarian catalogs the SIMs , and a SIM accounting system tracks { HEAD ~ and / bills } for { TAIL ~ SIM usage }
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