Transistor 168 has its emitter coupled to low voltage source A via {TAIL ~ resistor} 170, {HEAD ~ the combination} of which forms a current source 
of
Transistor 168 has its emitter coupled to low voltage source A via { TAIL ~ resistor } 170 , { HEAD ~ the combination } of which forms a current source
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH