Wagas, Ethel C., et al. “Biophysical Survey of the Hinatuan Enchanted River Underwater Cave System (HERUCS) and Its Connecting River, Surigao Del Sur, Southern Philippines”. Annals of Tropical Research, vol. 38, no. 1, July 2016, pp. 148-5, doi:10.32945/atr38112.2016.