In the past Ouargla was the center of trading of gold and slaves,[citation needed] as well as being an important center of Ibadi Islam. However, the Ibadis have left for the M'zab valley.
^Hamouda, A., 1980, Petroleum Potential-Ouargla Region Triassic Basin, Algeria, in Giant Oil and Gas Fields of the Decade: 1968-1978, AAPG Memoir 30, Halbouty, M.T., editor, Tulsa: American Association of Petroleum Geologists, ISBN0891813063, p. 539
^ abHamouda, A., 1980, Petroleum Potential-Ouargla Region Triassic Basin, Algeria, in Giant Oil and Gas Fields of the Decade: 1968-1978, AAPG Memoir 30, Halbouty, M.T., editor, Tulsa: American Association of Petroleum Geologists, ISBN0891813063, p. 540