Apparatus for establishing {HEAD ~ electrical conductivity} between {TAIL ~ a reference electrode} and soil under a pavement layer comprising: 
between
Apparatus for establishing { HEAD ~ electrical conductivity } between { TAIL ~ a reference electrode } and soil under a pavement layer comprising :
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH