diff --git a/sna/4_Social_Networks.ipynb b/sna/4_Social_Networks.ipynb
index b4c47f6..8b97bf9 100644
--- a/sna/4_Social_Networks.ipynb
+++ b/sna/4_Social_Networks.ipynb
@@ -808,7 +808,7 @@
     }
    },
    "source": [
-    "The notebook is freely licensed under under the [Creative Commons Attribution Share-Alike license](https://creativecommons.org/licenses/by/2.0/).  \n",
+    "The notebook is freely licensed under the [Creative Commons Attribution Share-Alike license](https://creativecommons.org/licenses/by/2.0/).  \n",
     "\n",
     "© Carlos A. Iglesias, Universidad Politécnica de Madrid."
    ]