Priatna, Priatna, and Eka Kadarsetia. 2007. “Characteristics of Volcanic Gas Correlated to the Eruption Activity; Case Study in the Merapi Volcano, Periods of 1990-1994”. Indonesian Journal on Geoscience 2 (4):235-46. https://doi.org/10.17014/ijog.2.4.235-246.