{HEAD ~ Collectors} or drains of {TAIL ~ the first and fourth transistors} are coupled together and collectors or drains of the second and third transistors are coupled together 
of
{ HEAD ~ Collectors } or drains of { TAIL ~ the first and fourth transistors } are coupled together and collectors or drains of the second and third transistors are coupled together
HEAD HEAD HEAD HEAD HEAD OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH