Etiope, G., Italiano, F., Favali, P. y Smriglio, G. 2002. Soil degassing at Ustica Island: Comparison between 1997 and 1999 surveys. Geofísica Internacional. 41, 3 (jul. 2002), 217–221. DOI:https://doi.org/10.22201/igeof.00167169p.2002.41.3.333.