Nguyen, Thi Diem Trinh, et al. “Treating Coffee Grounds and Its Application As Substrates for Water Spinach (Ipomoea Aquatic) Growth in Hydroponic System”. Dong Thap University Journal of Science, vol. 9, no. 3, June 2020, pp. 73-79, doi:10.52714/dthu.9.3.2020.793.