Taran, Yuri, et al. “Chemical Precursors to the 1998-1999 Eruption of Colima Volcano, Mexico”. Revista Mexicana De Ciencias Geológicas, vol. 17, no. 2, July 2018, pp. 111-24, https://rmcg.unam.mx/index.php/rmcg/article/view/1006.