Independent Petroleum Association of America. (1971). Petroleum independent. Independent Petroleum Association of America].
Chicago-referens (17:e uppl.)Independent Petroleum Association of America. Petroleum Independent. [Tulsa, Okla.: Independent Petroleum Association of America], 1971.
MLA-referens (8:e uppl.)Independent Petroleum Association of America. Petroleum Independent. Independent Petroleum Association of America], 1971.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.