added link to the article
@@ -49,7 +49,9 @@ class NormalizedDifferenceIndexTask(MapFeatureTask):
:math:`NDI = \\dfrac{A-B+c}{A+B+c}`,
- where c is provided as the *constant* argument.
+ where c is provided as the *constant* argument. For the reasoning behind using the constant in the equation,
+ check the article `Using NDVI with atmospherically corrected data
+ <http://www.cesbio.ups-tlse.fr/multitemp/?p=12746>`_.
"""
def __init__(self, input_feature, output_feature, bands, constant=0, undefined_value=np.nan):
