{HEAD ~ An internal combustion engine} is provided having {TAIL ~ a pair} of cylinders interconnected by means of a narrow connecting channel 
{ HEAD ~ An internal combustion engine } is provided having { TAIL ~ a pair } of cylinders interconnected by means of a narrow connecting channel
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH