VREF is fed back to {HEAD ~ the bases} of {TAIL ~ transistors} 106 and 108 
VREF is fed back to { HEAD ~ the bases } of { TAIL ~ transistors } 106 and 108
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH