The present invention provides an air-fuel ratio feedback control apparatus for an internal-combustion engine. The apparatus includes an air-fuel ratio detector that is disposed in an exhaust system of the engine so as to detect an air-fuel ratio of exhaust gas, NOx purifier for purifying NOx contained...http://www.google.com.au/patents/US6739122?utm_source=gb-gplus-sharePatent US6739122 - Air-fuel ratio feedback control apparatus
