diff --git a/python-core/structs_utils.ipynb b/python-core/structs_utils.ipynb
index 5f7e18a..e719c9f 100644
--- a/python-core/structs_utils.ipynb
+++ b/python-core/structs_utils.ipynb
@@ -1,7 +1,7 @@
 {
  "metadata": {
   "name": "",
-  "signature": "sha256:fed6792b1275b1a5b92e846b93e797942c4eac23ccf1c44b750b469e3f33ffbe"
+  "signature": "sha256:2c46d8f6939d7b4d055f9656cc26509f03ad920ea06c57a8675dedc7faa93597"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -48,7 +48,9 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "![alt text](http://www.nltk.org/images/string-slicing.png)"
+      "![alt text](http://www.nltk.org/images/string-slicing.png)\n",
+      "\n",
+      "Image source: http://www.nltk.org/images/string-slicing.png"
      ]
     },
     {