Arifin, A., D. Karam, J. Shamshuddin, N. Majid, O. Radziah, A. Hazandy, and I. Zahari. “Proposing a Suitable Soil Quality Index for Natural, Secondary and Rehabilitated Tropical Forests in Malaysia”. African Journal of Biotechnology, vol. 11, no. 14, Feb. 2014, pp. 3297-09, doi:10.5897/ajb11.2903.