diff --git a/graphs_trees/tree_dfs/dfs_challenge.ipynb b/graphs_trees/tree_dfs/dfs_challenge.ipynb
index 5c12580..1748729 100644
--- a/graphs_trees/tree_dfs/dfs_challenge.ipynb
+++ b/graphs_trees/tree_dfs/dfs_challenge.ipynb
@@ -65,7 +65,7 @@
    "source": [
     "## Algorithm\n",
     "\n",
-    "Refer to the [solution notebook](https://github.com/donnemartin/interactive-coding-challenges/graphs_trees/tree_dfs/dfs_solution.ipynb).  If you are stuck and need a hint, the solution notebook's algorithm discussion might be a good place to start."
+    "Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/tree_dfs/dfs_solution.ipynb).  If you are stuck and need a hint, the solution notebook's algorithm discussion might be a good place to start."
    ]
   },
   {
@@ -197,17 +197,8 @@
    "source": [
     "## Solution Notebook\n",
     "\n",
-    "Review the [solution notebook](https://github.com/donnemartin/interactive-coding-challenges/graphs_trees/tree_dfs/dfs_solution.ipynb) for a discussion on algorithms and code solutions."
+    "Review the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/graphs_trees/tree_dfs/dfs_solution.ipynb) for a discussion on algorithms and code solutions."
    ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "metadata": {
-    "collapsed": true
-   },
-   "outputs": [],
-   "source": []
   }
  ],
  "metadata": {