The intake and exhaust valves alternately and selectively opens and closes, and simultaneously openes during a valve overlap period, in synchronism with a rotation of a crankshaft to open the passages to the combustion chamber, wherein said {HEAD ~ apparatus} controls {TAIL ~ a valve timing} of the intake valve and the valve timing of the exhaust valve in accordance with a running condition of the engine 
controls
The intake and exhaust valves alternately and selectively opens and closes , and simultaneously openes during a valve overlap period , in synchronism with a rotation of a crankshaft to open the passages to the combustion chamber , wherein said { HEAD ~ apparatus } controls { TAIL ~ a valve timing } of the intake valve and the valve timing of the exhaust valve in accordance with a running condition of the engine
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