Marbun, Mahmuddin, Sismanto Sismanto, Zuhrahmi DE, Imran Tarique, and Punhoon Khan Korai. “Identification of Underground River Flow Using VLF (Very Low Frequency) and Geoelectricity at Karstic Area”. International Journal of Hydrological and Environmental for Sustainability 2, no. 3 (October 28, 2023): 130–147. Accessed February 4, 2026. https://journal.foundae.com/index.php/ijhes/article/view/332.