APA

Watkins G. C., University of Calgary, World Petroleum Congress (13th. : 1991 : Buenos Aires) & University of Calgary.The United States-Canada free trade agreement. : .

Chicago

Watkins G C, University of Calgary, World Petroleum Congress (13th. : 1991 : Buenos Aires) and University of Calgary.The United States-Canada free trade agreement. : .

Harvard

Watkins G. C., University of Calgary, World Petroleum Congress (13th. : 1991 : Buenos Aires) and University of Calgary.The United States-Canada free trade agreement. : .

MLA

Watkins G C, University of Calgary, World Petroleum Congress (13th. : 1991 : Buenos Aires) and University of Calgary.: . .