Polarization of tremor wavefield at mount Etna and some open questions on type and dynamics of the source:comparison between the 1989 and 1991-1993 eruptions
R. Napoli et al., Polarization of tremor wavefield at mount Etna and some open questions on type and dynamics of the source:comparison between the 1989 and 1991-1993 eruptions, Acta vulcanologica AV. Acta vulcanologica , 4, 1994, pp. 57-62