García-Vindas, J. R., Fernández, E., Duarte, E., & Malavassi, E. (2002). Radon concentration anomalies as possible precursors to pyroclastic flow events of Arenal volcano. Geofísica Internacional, 41(4), 475–481. https://doi.org/10.22201/igeof.00167169p.2002.41.4.497