G. M. S. Hutabarat, B. W. Simanihuruk, C. Herison, Z. Muktamar, and P. M. Hairani, “The Effect of Ultisols Subsoil Combined with Mexican Sunflower (Tithonia diversifolia) Compost and Vermicompost on Pre-Nursery Growth of Oil Palm Seedling”, Akta Agrosia, vol. 26, no. 2, pp. 50–58, Dec. 2023.