diff --git a/ml4/2_5_1_Exercise.ipynb b/ml4/2_5_1_Exercise.ipynb
index 70cd129..70351f9 100644
--- a/ml4/2_5_1_Exercise.ipynb
+++ b/ml4/2_5_1_Exercise.ipynb
@@ -206,7 +206,7 @@
     "\n",
     "Since there is a problem with Scikit version 0.24, you can just comment on the different approaches.",
     "\n",
-    "Alternatively, you can also use  the library [sklearn-genetic-opt](https://sklearn-genetic-opt.readthedocs.io/en/stable/index.html) and discuss the digit classification example included in the library."
+    "Alternatively, you can also use  the library [sklearn-genetic-opt](https://sklearn-genetic-opt.readthedocs.io/en/stable/index.html) and discuss the digit classification example included in the library: [digits decision tree](https://sklearn-genetic-opt.readthedocs.io/en/stable/notebooks/Digits_decision_tree.html)."
    ]
   },
   {