Wendy Tarigan, Kristianus Oktriono. “A PRELIMINARY STUDY OF SUSTAINABLE TOURISM DEVELOPMENT: A CASE STUDY IN TOBA REGION”. PalArch’s Journal of Archaeology of Egypt / Egyptology, vol. 18, no. 1, Dec. 2020, pp. 78 -8, http://mail.palarch.nl/index.php/jae/article/view/2012.