Arrays of such sensors are constructed with {HEAD ~ at least two sensors} having {TAIL ~ different chemically sensitive resistors} providing dissimilar such differences in resistance 
having
Arrays of such sensors are constructed with { HEAD ~ at least two sensors } having { TAIL ~ different chemically sensitive resistors } providing dissimilar such differences in resistance
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH