An engine comprising an exhaust passage having therein a NO.sub.x absorbent which absorbs the NO.sub.x when the air-fuel ratio of the exhaust gas flowing into the NO.sub.x absorbent is lean and releases the absorbed NO.sub.x when the concentration of oxygen in the exhaust gas is lowered. When the air-fuel...http://www.google.fr/patents/US5388403?utm_source=gb-gplus-shareBrevet US5388403 - Exhaust gas purification device for an engine
