title: Air quality in selected urban areas 1977-1978. WHO Collaborating Centre on Environmental Pollution Control, United States Environmental Protection Agency, Washington, DC, USA.
mesh_terms: D000397:Air Pollution / Q000032:analysis; D012906:Smoke / Q000032:analysis*; D013458:Sulfur Dioxide / Q000032:analysis*; D014944:World Health Organization
chemical_list: D012906:Smoke; D013458:Sulfur Dioxide