Aflizar, ., . Muzakkir, R. Afrizal, and M. A. Rahman. “Geochemical Investigation of Selected Elements in an Agricultural Soil: Case Study in Sumani Watershed West Sumatera in Indonesia”. JOURNAL OF TROPICAL SOILS, vol. 21, no. 1, Jan. 2017, pp. 49-66, doi:10.5400/jts.2016.v21i1.49-66.