Barragán, R. and Maurrasse, F.J.-M.R. 2018. Lower Aptian (Lower Cretaceous) ammonites from the basal strata of the La Peña Formation of Nuevo León State, northeast Mexico: biochronostratigraphic implications. Revista Mexicana de Ciencias Geológicas. 25, 1 (Jan. 2018), 145–157.