Kongroy, P., Pinawet, T. and Peerachaakkarachai, K. 2026. Development and Upgrading of Organic Fertilizer Products Using Circular Economy Concept to Empower the Na Ngua Organic Agriculture Group, Phetchabun Province. The Golden Teak : Science and Technology Journal (GTSJ.). 13, 1 (Aug. 2026), 38–55.