APA

Willmon G. J., Esso, World Petroleum Congress (12th : 1987 26 abr/1 may : Houston) & ESSO.Economic outlook for extra-heavy oils, natural bitumens and shale oils. : .

Chicago

Willmon Gordon J, Esso, World Petroleum Congress (12th : 1987 26 abr/1 may : Houston) and ESSO.Economic outlook for extra-heavy oils, natural bitumens and shale oils. : .

Harvard

Willmon G. J., Esso, World Petroleum Congress (12th : 1987 26 abr/1 may : Houston) and ESSO.Economic outlook for extra-heavy oils, natural bitumens and shale oils. : .

MLA

Willmon Gordon J, Esso, World Petroleum Congress (12th : 1987 26 abr/1 may : Houston) and ESSO.: . .