Dyfyniad APA
Global Environmental Monitoring System. (1991). Urban air pollution. United nations environment health.
Dyfyniad Arddull Chicago
Global Environmental Monitoring System. Urban Air Pollution. Nairobi: United nations environment health, 1991.
Dyfyniad MLA
Global Environmental Monitoring System. Urban Air Pollution. United nations environment health, 1991.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.