diff --git a/graphs_trees/graph/graph_challenge.ipynb b/graphs_trees/graph/graph_challenge.ipynb
index c8a7db7..b462371 100644
--- a/graphs_trees/graph/graph_challenge.ipynb
+++ b/graphs_trees/graph/graph_challenge.ipynb
@@ -4,7 +4,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges)."
+    "This notebook was prepared by [Donne Martin](https://github.com/donnemartin) and [Kevin Chan](https://github.com/kevinxchan). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges)."
    ]
   },
   {
@@ -145,11 +145,11 @@
     "        # TODO: Implement me\n",
     "        pass\n",
     "\n",
-    "    def add_edge(self, source, dest, weight=0):\n",
+    "    def add_edge(self, source_key, dest_key, weight=0):\n",
     "        # TODO: Implement me\n",
     "        pass\n",
     "\n",
-    "    def add_undirected_edge(self, source, dest, weight=0):\n",
+    "    def add_undirected_edge(self, source_key, dest_key, weight=0):\n",
     "        # TODO: Implement me\n",
     "        pass"
    ]
diff --git a/graphs_trees/graph/graph_solution.ipynb b/graphs_trees/graph/graph_solution.ipynb
index ddfe0ae..694ee53 100644
--- a/graphs_trees/graph/graph_solution.ipynb
+++ b/graphs_trees/graph/graph_solution.ipynb
@@ -4,7 +4,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges)."
+    "This notebook was prepared by [Donne Martin](https://github.com/donnemartin) and [Kevin Chan](https://github.com/kevinxchan). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges)."
    ]
   },
   {
@@ -153,19 +153,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
-   "metadata": {
-    "collapsed": false
-   },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "Overwriting graph.py\n"
-     ]
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%%writefile graph.py\n",
     "from enum import Enum  # Python 2 users: Run pip install enum34\n",
@@ -231,19 +221,17 @@
     "            self.add_node(dest_key)\n",
     "        self.nodes[source_key].add_neighbor(self.nodes[dest_key], weight)\n",
     "\n",
-    "    def add_undirected_edge(self, src_key, dst_key, weight=0):\n",
+    "    def add_undirected_edge(self, source_key, dest_key, weight=0):\n",
     "        if src_key is None or dst_key is None:\n",
     "            raise TypeError('key cannot be None')\n",
-    "        self.add_edge(src_key, dst_key, weight)\n",
-    "        self.add_edge(dst_key, src_key, weight)"
+    "        self.add_edge(source_key, dest_key, weight)\n",
+    "        self.add_edge(dest_key, source_key, weight)"
    ]
   },
   {
    "cell_type": "code",
    "execution_count": 2,
-   "metadata": {
-    "collapsed": false
-   },
+   "metadata": {},
    "outputs": [],
    "source": [
     "%run graph.py"
@@ -258,19 +246,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 3,
-   "metadata": {
-    "collapsed": false
-   },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "Overwriting test_graph.py\n"
-     ]
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%%writefile test_graph.py\n",
     "from nose.tools import assert_equal\n",
@@ -351,9 +329,7 @@
   {
    "cell_type": "code",
    "execution_count": 4,
-   "metadata": {
-    "collapsed": false
-   },
+   "metadata": {},
    "outputs": [
     {
      "name": "stdout",
@@ -389,5 +365,5 @@
   }
  },
  "nbformat": 4,
- "nbformat_minor": 0
+ "nbformat_minor": 1
 }