2004 North American Commission on Stratigraphic Nomenclature (2005). «North American Stratigraphic Code». American Association of Petroleum Geologists Bulletin, v. 89, no. 11: 1567-1570. Consultado el 13 de junio de 2020. «The wedge-out of a component formation or formations may justify the reduction of a group to formation rank, retaining the same name.»