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