Omaña, Lourdes, et al. “Barremian Planktonic Foraminiferal Events Correlated With the Ammonite Zones from the San Lucas Formation, Michoacán (SW Mexico)”. Revista Mexicana De Ciencias Geológicas, vol. 22, no. 1, May 2018, pp. 88-96, https://rmcg.unam.mx/index.php/rmcg/article/view/875.