Winarno, Gunardi D., Ricky Avenzora, Sambas Basuni, and M Bismark. 2015. “The Planning of Ecotourism Opportunities Spectrum of Elephant Related Ecotourism Activities on Sumatran Elephant Home Range in Bukit Barisan Selatan National Park Province Lampung Indonesia”. International Journal of Sciences: Basic and Applied Research (IJSBAR) 22 (2):130-48. https://gssrr.org/index.php/JournalOfBasicAndApplied/article/view/3947.