{HEAD ~ Neither the first input signal} nor the second input signal are applied to {TAIL ~ a base} or gate of the fourth transistor 
applied to
{ HEAD ~ Neither the first input signal } nor the second input signal are applied to { TAIL ~ a base } or gate of the fourth transistor
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH