Burrell, G. A.; Robertson, I. W. & Oberfell, G. G. Black Damp in Mines. Washington D.C.. UNT Digital Library. http://digital.library.unt.edu/ark:/67531/metadc12312/. Accessed December 8, 2013.
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.