Connor, C. B. “Anomalous Soil Mercury Concentrations at Paricutin Volcano, Michoacan - Guanajuato Volcanic Field. Mexico”. Geofisica Internacional, vol. 28, no. 5, Dec. 1989, pp. 1029-41, doi:10.22201/igeof.00167169p.1989.28.5.1296.