Assessment of the humification degree of peat soil under sago (Metroxylon sagu) cultivation based on Fourier Transform Infrared (FTIR) and Ultraviolet-Visible (UV-Vis) spectroscopi... oleh S.F. Sim, M.E. Wasli, C.M.R. Yong, P.S. Howell, C. Jumin, N.A. Safie, B. Samling