Barkley, J. F. Accepted Limit Values of Air Pollutants. Washington D.C.. UNT Digital Library. http://digital.library.unt.edu/ark:/67531/metadc67065/. Accessed August 22, 2014.
Note: Inconsistencies in capitalization and punctuation within the Digital Library may affect this citation. Before using this citation in formal writing, please consult your preferred style manual. More information.