Heine, Klaus. “Paleopedological Evidence of Human-Induced Environmental Change in the Puebla – Tlaxcala Area (Mexico) During the Last 3,500 Years”. Revista Mexicana De Ciencias Geológicas, vol. 20, no. 3, May 2018, pp. 235-44, https://rmcg.geociencias.unam.mx/index.php/rmcg/article/view/923.