Volcanic SO2 by UV-TIR satellite retrievals: validation by using ground-based network at Mt. Etna oleh Claudia Spinetti, Giuseppe Giovanni Salerno, Tommaso Catalbiano, Elisa Carboni, Lieven Clarisse, Stefano Corradini, Roy Gordon Grainger, Pascal Andre Hedelt, Maria Elissavet Koukouli, Luca Merucci, Richard Siddans, Lucia Tampellini, Nicolas Theys, Pieter Valks, Claus Zehner