APA Format
World Health Organization (WHO) . (). Air quality criteria and guides for urban air pollutants, TRS.506. : Geneva WHO 1972
MLA Format
World Health Organization (WHO) . Air quality criteria and guides for urban air pollutants, TRS.506. : Geneva WHO 1972,
Australian/Harvard Format
World Health Organization (WHO) . . Air quality criteria and guides for urban air pollutants, TRS.506. Geneva WHO 1972, 
Warning: These citations may not always be 100% accurate.