D. D. Siskawardani, J. . Onthong, . K. Khawmee, and C. . Poonpakdee, “Manganese status in upland and lowland rubber-growing soils in Songkhla province, southern Thailand”, Agr. Nat. Resour., vol. 50, no. 4, pp. 321–325, Aug. 2016.