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