Tassi, Franco et al. "Gas discharges from four remote volcanoes in northern Chile (Putana, Olca, Irruputuncu and Alitar): a geochemical survey." Annals of Geophysics 54.2 (2011).
(PDF)
sciencedirect.com
Stebel, Kerstin et al. "First estimates of fumarolic SO 2 fluxes from Putana volcano, Chile, using an ultraviolet imaging camera." Journal of Volcanology and Geothermal Research 300 (2015): 112-120.
(online)