Al Barrak، K. M.، و Rowell، D. (2000). The Weathering of Gypsum and Calcite and their Role in the Reclamation of Soils from Al-Hassa Oasis, Saudi Arabia (رسالة دكتوراه غير منشورة). University of Reading، ريدنج. مسترجع من http://search.mandumah.com/Record/608303
Al Barrak، Khalid Mohamed، و David Rowell. "The Weathering of Gypsum and Calcite and Their Role in the Reclamation of Soils From Al-Hassa Oasis, Saudi Arabia" رسالة دكتوراه. University of Reading، ريدنج، 2000. مسترجع من http://search.mandumah.com/Record/608303