diff --git a/rtd/source/conf.py b/rtd/source/conf.py
index a0edc2eb02c25677ff9dca4d1def4bb986b72367..7623d803ab3e7f7cb0590d6670d632d52bf5377e 100644
--- a/rtd/source/conf.py
+++ b/rtd/source/conf.py
@@ -15,11 +15,6 @@ import os
 import sys
 sys.path.insert(0, os.path.abspath('..'))
 
-# math
-from sphinx_math_dollar import NODE_BLACKLIST
-from docutils.nodes import header,FixedTextElement, literal,math
-from docutils.nodes import  comment, doctest_block, image, literal_block, math_block, paragraph, pending, raw, rubric, substitution_definition, target
-math_dollar_node_blacklist = (literal,math,doctest_block, image, literal_block,  math_block,  pending,  raw,rubric, substitution_definition,target)
 # -- General configuration ---------------------------------------------------
 # https://www.sphinx-doc.org/en/master/usage/configuration.html#general-configuration
 
@@ -30,6 +25,10 @@ exclude_patterns = []
 
 autodoc_member_order = 'bysource'
 
+# math
+from sphinx_math_dollar import NODE_BLACKLIST
+from docutils.nodes import header,FixedTextElement, literal,math
+from docutils.nodes import  comment, doctest_block, image, literal_block, math_block, paragraph, pending, raw, rubric, substitution_definition, target
 mathjax_config = {
     'tex2jax': {
         'inlineMath': [ ["\\(","\\)"] ],
diff --git a/sen2chain/indices.py b/sen2chain/indices.py
index 7a967457b1ab780a13fa5d61a2cdbb492466a24c..530bff9363e10e544420b93c9f154dd4e0621419 100644
--- a/sen2chain/indices.py
+++ b/sen2chain/indices.py
@@ -69,7 +69,9 @@ class Indice(metaclass=ABCMeta):
 
 class Ndvi(Indice):
     """
-    $$NDVI = {{NIR-VIR}\over{NIR+VIR}}$$
+
+    .. math::
+        {NDVI = {NIR-VIR}\over{NIR+VIR}}
 
     NIR: band 08 (10m)
     VIR: band 04 (10m)