Kay Thi Khaing, Chongchin Polprasert, and Suwisa Mahasandana. “Phosphorus Extraction from Waste Activated Sludge Using Sulfuric Acid Leaching: Recovery P and Reduction P Leakage”. International Journal of Scientific Research and Innovative Studies, vol. 1, no. 2, Sept. 2022, pp. 111-6, https://www.ijsrisjournal.com/index.php/ojsfiles/article/view/65.