Parkhurst & Oliff
Exhaust gas purifying method of an internal combustion engine
 At least one electrical signal which indicates an operating condition of an internal combustion engine is generated, and then a first air-fuel ratio feedback control system which controls a carburetor air-fuel ratio and a second air-fuel ratio feedback control system which controls the amount of secondary air supplied into the exhaust system is selectively energized so as to function in accordance with the generated electrical signal. 
Toyota Jidosha Kogyo Kabushiki Kaisha
Y F F F F
Y02A F01N F02D F01N F01N
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Kichiro Michiaki
Kato Ujihashi