Permutation entropy variation for 2007 effusive dome-forming eruption period of Kelud Volcano, IndonesiaLusia Rita Nugraheni, Agung Harijoko, Wiwit Suryanto and Hetty TriastutyE3S Web Conf., 325 (2021) 01010DOI: https://doi.org/10.1051/e3sconf/202132501010