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FILE - Billionaire oilman Harold Hamm stands for a portrait by an oil rig near Watford City, N.D., on April 30, 2009. (AP Photo/James MacPherson, File)
FILE - Billionaire oilman Harold Hamm stands for a portrait by an oil rig near Watford City, N.D., on April 30, 2009. (AP Photo/James MacPherson, File)