...Producing Inc., Union Oil Co. of California, NGC Energy Co., Bogert Oil Co., Kaiser Francis Oil Co., Seneca Oil Co., Unit Drilling and Exploration Co., Viersen Cochran, Mustang Fuel Corp., Oryx Energy Co...., Mesa Midcontinent Co., Texaco Exploration Production Inc., PG E Resources Co., Louis Dreyfus Nat. Gas Corp., Unit Petroleum Co., Bracken Energy...Mustang Production Co., Amoco Production Co., Anson Corp., Apache Corp., Conoco Inc., Phillips Petroleum Co., Sun Exploration and Production, Mesa Midcontinent Ltd. Partnership, Texaco Inc., Texaco...