Air 4 Aire 4 Contaminacio ́n 4 Historia 4 Pollution 4 Air Pollution 3 Condiciones econo ́micas 3 Hazardous wastes 3 History 3 Poli ́tica y gobierno 3 Air quality management 2 Antiguedades 2 Antiquities 2 Archeologie 2 Comercio 2 Commerce 2 Conditions e ́conomiques 2 Diplomatic relations 2 Economic conditions 2 Economic history 2 FOREIGN RELATIONS 2 Finance 2 Foreign relations 2 HISTORIA 2 Hazardous Waste 2 Histoire 2 International relations 2 Management 2 PUBLICACIONES PERIODICAS 2 Pe ́riodiques 2