Hidayati, Nur Aini. “Estimating Willingness-to-Pay Values to Improve the PDAM Clean Water in Surabaya”. International Journal of Psychosocial Rehabilitation 24, no. 7 (September 30, 2020): 786–799. Accessed March 3, 2026. https://psychosocial.com/index.php/ijpr/article/view/9595.