Reference:

Clark, R.N., Swayze, G.A., Wise, R., Livo, E., Hoefen, T., Kokaly, R.,
Sutley, S.J.,  2007, USGS digital spectral library splib06a: 
U.S. Geological Survey, Digital Data Series 231,
http://speclab.cr.usgs.gov/spectral.lib06.

             U.S. Geological Survey, MS 964
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                    rclark@usgs.gov
