MONDAL, BHABANI PRASAD, et al. “Rapid Prediction of Soil Available Sulphur Using Visible Near-Infrared Reflectance Spectroscopy”. The Indian Journal of Agricultural Sciences, vol. 91, no. 9, Sept. 2021, pp. 1328–1332, https://doi.org/10.56093/ijas.v91i9.116080.