diff --git a/docs/modules/arm_navigation.rst b/docs/modules/arm_navigation.rst
index a9721def..ba84f033 100644
--- a/docs/modules/arm_navigation.rst
+++ b/docs/modules/arm_navigation.rst
@@ -13,7 +13,7 @@ This is a interactive simulation.
 You can set the goal position of the end effector with left-click on the
 ploting area.
 
-`Documentation <PythonRobotics/arm_obstacle_navigation.py at master · AtsushiSakai/PythonRobotics https://github.com/AtsushiSakai/PythonRobotics/blob/master/ArmNavigation/arm_obstacle_navigation/arm_obstacle_navigation.py>`_
+Check this doc for machematical background: `Jupyter notebook documentation <https://github.com/AtsushiSakai/PythonRobotics/blob/master/ArmNavigation/arm_obstacle_navigation/arm_obstacle_navigation.py>`_
 
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