Barragán-Manzo, Ricardo, and Ana Laura Méndez-Franco. 2018. “Towards a Standard Ammonite Zonation for the Aptian (Lower Cretaceous) of Northern Mexico”. Revista Mexicana De Ciencias Geológicas 22 (1):39-47. https://www.rmcg.unam.mx/index.php/rmcg/article/view/872.