The second input signal is applied to a base or gate of {HEAD ~ the third transistor} with {TAIL ~ regard} to the reference point 
The second input signal is applied to a base or gate of { HEAD ~ the third transistor } with { TAIL ~ regard } to the reference point
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH