diff --git a/pandas/pandas_clean.ipynb b/pandas/pandas_clean.ipynb
index ff7d3cc..69d8c37 100644
--- a/pandas/pandas_clean.ipynb
+++ b/pandas/pandas_clean.ipynb
@@ -1,7 +1,7 @@
 {
  "metadata": {
   "name": "",
-  "signature": "sha256:a3874e8de1273dccf0e0d39f584d1345a1c1d55f2b6c1ad780fedce8f9421bcf"
+  "signature": "sha256:82be3772f18b2c96a1486b76adf812e774890e366b350dfd5b1257ab4b086b8e"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -16,7 +16,8 @@
       "* Clean\n",
       "* Transform\n",
       "* Merge\n",
-      "* Reshape"
+      "* Reshape\n",
+      "* Concatenate"
      ]
     },
     {
@@ -35,7 +36,7 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "Replace all occurrences of a string with another string, in place (no copy):"
+      "Check for matching values in a specific column for replacement:"
      ]
     },
     {
@@ -113,6 +114,70 @@
      ],
      "prompt_number": 2
     },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "df_1[df_1['state'] == 'VA']"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "html": [
+        "<div style=\"max-height:1000px;max-width:1500px;overflow:auto;\">\n",
+        "<table border=\"1\" class=\"dataframe\">\n",
+        "  <thead>\n",
+        "    <tr style=\"text-align: right;\">\n",
+        "      <th></th>\n",
+        "      <th>pop</th>\n",
+        "      <th>state</th>\n",
+        "      <th>year</th>\n",
+        "    </tr>\n",
+        "  </thead>\n",
+        "  <tbody>\n",
+        "    <tr>\n",
+        "      <th>0</th>\n",
+        "      <td> 5.0</td>\n",
+        "      <td> VA</td>\n",
+        "      <td> 2012</td>\n",
+        "    </tr>\n",
+        "    <tr>\n",
+        "      <th>1</th>\n",
+        "      <td> 5.1</td>\n",
+        "      <td> VA</td>\n",
+        "      <td> 2013</td>\n",
+        "    </tr>\n",
+        "    <tr>\n",
+        "      <th>2</th>\n",
+        "      <td> 5.2</td>\n",
+        "      <td> VA</td>\n",
+        "      <td> 2014</td>\n",
+        "    </tr>\n",
+        "  </tbody>\n",
+        "</table>\n",
+        "</div>"
+       ],
+       "metadata": {},
+       "output_type": "pyout",
+       "prompt_number": 3,
+       "text": [
+        "   pop state  year\n",
+        "0  5.0    VA  2012\n",
+        "1  5.1    VA  2013\n",
+        "2  5.2    VA  2014"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Replace all occurrences of a string with another string, in place (no copy):"
+     ]
+    },
     {
      "cell_type": "code",
      "collapsed": false,
@@ -172,7 +237,7 @@
        ],
        "metadata": {},
        "output_type": "pyout",
-       "prompt_number": 3,
+       "prompt_number": 4,
        "text": [
         "   pop     state  year\n",
         "0  5.0  VIRGINIA  2012\n",
@@ -183,7 +248,7 @@
        ]
       }
      ],
-     "prompt_number": 3
+     "prompt_number": 4
     },
     {
      "cell_type": "markdown",
@@ -196,7 +261,8 @@
      "cell_type": "code",
      "collapsed": false,
      "input": [
-      "df_1.replace({'state' : { 'MD' : 'MARYLAND' }})"
+      "df_1.replace({'state' : { 'MD' : 'MARYLAND' }})\n",
+      "df_1"
      ],
      "language": "python",
      "metadata": {},
@@ -250,7 +316,7 @@
        ],
        "metadata": {},
        "output_type": "pyout",
-       "prompt_number": 4,
+       "prompt_number": 5,
        "text": [
         "   pop     state  year\n",
         "0  5.0  VIRGINIA  2012\n",
@@ -261,7 +327,7 @@
        ]
       }
      ],
-     "prompt_number": 4
+     "prompt_number": 5
     }
    ],
    "metadata": {}