In situ measurements of soil colour, mineral composition and clay content by vis-NIR spectroscopy Viscarra Rossel, R. A. ; Cattle, S. R. ; Ortega, A. ; Fouad, Y. Abstract Publication: Geoderma Pub Date: May 2009 DOI: 10.1016/j.geoderma.2009.01.025 Bibcode: 2009Geode.150..253V