Prol Ledesma, R. M., Medina, F., Choporov, D. Y., Frikh K., D. I., Muravitskaya, G. N., Polak, B. G., & Stepanets, M. I. (1982). Preliminary chemical and petrographic results of the march-april "El Chichon" volcanics. Geofísica Internacional, 21(1), 1–10. https://doi.org/10.22201/igeof.00167169p.1982.21.1.1073