https://doi.org/10.3390/rs61110813
Nawar, S., Buddenbaum, H., Hill, J., Kozak, J. & Mouazen, A. M. (2016).
Estimating the soil clay content and organic matter by means of
different calibration methods of vis-NIR diffuse reflectance
spectroscopy. Soil and Tillage Research , 155, 510-522.