A. Al-Hasson and Yasser H. Kaddo, M. and D. Nader, A. 2007. A Detail Study of the Genus Vallatisporites as a Lower Carboniferous Stratigraphic and Paleogeographic Indicator. Iraqi National Journal of Earth Science (INJES). 7, 2 (Dec. 2007), 73–96. DOI:https://doi.org/10.33899/earth.2007.39273.