Hartono, Hill. G., Teguh Wage Prakoso, Danu Wahyu Dalio, and Alfred Steven. “Studi Awal Keberadaan Gunung Api Purba Tulakan-Ketro, Pacitan, Jawa Timur”. ReTII00 (January 15, 2017). Accessed July 3, 2024. //journal.itny.ac.id/index.php/ReTII/article/view/267.