diff --git a/hacker-rank/maximizing-xor.ipynb b/hacker-rank/maximizing-xor.ipynb
index 2ef336a..58e6e1f 100644
--- a/hacker-rank/maximizing-xor.ipynb
+++ b/hacker-rank/maximizing-xor.ipynb
@@ -1,5 +1,12 @@
 {
  "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "<small><i>This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://bit.ly/code-notes).</i></small>"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},
@@ -77,7 +84,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython2",
-   "version": "2.7.9"
+   "version": "2.7.10"
   }
  },
  "nbformat": 4,
diff --git a/hacker-rank/utopian-tree.ipynb b/hacker-rank/utopian-tree.ipynb
index 5915377..4a9844a 100644
--- a/hacker-rank/utopian-tree.ipynb
+++ b/hacker-rank/utopian-tree.ipynb
@@ -1,5 +1,12 @@
 {
  "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "<small><i>This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://bit.ly/code-notes).</i></small>"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},
@@ -83,7 +90,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython2",
-   "version": "2.7.9"
+   "version": "2.7.10"
   }
  },
  "nbformat": 4,