Manik, Charla Tri Selda. “Measurement of Earth Value Using Earth Tester Measurement at Efarina University”. Journal of Science Technology (JoSTec) 2, no. 1 (December 28, 2020): 42–47. Accessed May 4, 2024. https://ejournal.ipinternasional.com/index.php/jostec/article/view/51.