Gaya APA

Leffler, W, L. (2009). Petroleum refining in nontechnical language 4 : refinery gas plants / cat reforming (4). New York: .

Gaya MLA

Leffler, William, L.. "Petroleum refining in nontechnical language 4 : refinery gas plants / cat reforming". 4 New York: , 2009. Multimedia.