{HEAD ~ A three dimensional crossbar array} may include {TAIL ~ a metal layer}, and an insulator layer disposed adjacent the metal layer 
{ HEAD ~ A three dimensional crossbar array } may include { TAIL ~ a metal layer } , and an insulator layer disposed adjacent the metal layer
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH