Resistors R located between the non inverting terminals of op amps 68 and 70 to voltage sources V2 provide {TAIL ~ balanced impedences} to {HEAD ~ the op amp terminals} 
Resistors R located between the non inverting terminals of op amps 68 and 70 to voltage sources V2 provide { TAIL ~ balanced impedences } to { HEAD ~ the op amp terminals }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD