diff --git a/.ipynb_checkpoints/palindrome_timeit-checkpoint.ipynb b/.ipynb_checkpoints/palindrome_timeit-checkpoint.ipynb
new file mode 100644
index 0000000..b6b7c8a
--- /dev/null
+++ b/.ipynb_checkpoints/palindrome_timeit-checkpoint.ipynb
@@ -0,0 +1,165 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:710150d6bf8fe09c3a2348c765457cdea364ebe260d10f57be9349b32ef3ff50"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Sebastian Raschka 04/2014\n",
+      "\n",
+      "#Timing different Implementations of palindrome functions"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "import re\n",
+      "import timeit\n",
+      "import string\n",
+      "\n",
+      "# All functions return True if an input string is a palindrome. Else returns False.\n",
+      "\n",
+      "\n",
+      "\n",
+      "####\n",
+      "#### case-insensitive ignoring punctuation characters\n",
+      "####\n",
+      "\n",
+      "def palindrome_short(my_str):\n",
+      "    stripped_str = \"\".join(l.lower() for l in my_str if l.isalpha())\n",
+      "    return stripped_str == stripped_str[::-1]\n",
+      "\n",
+      "def palindrome_regex(my_str):\n",
+      "    return re.sub('\\W', '', my_str.lower()) == re.sub('\\W', '', my_str[::-1].lower())\n",
+      "\n",
+      "def palindrome_stringlib(my_str):\n",
+      "    LOWERS = set(string.ascii_lowercase)\n",
+      "    letters = [c for c in my_str.lower() if c in LOWERS]\n",
+      "    return letters == letters[::-1]\n",
+      "\n",
+      "####\n",
+      "#### functions considering all characters (case-sensitive)\n",
+      "####\n",
+      "\n",
+      "def palindrome_reverse1(my_str):\n",
+      "    return my_str == my_str[::-1]\n",
+      "\n",
+      "def palindrome_reverse2(my_str):\n",
+      "    return my_str == ''.join(reversed(my_str))\n",
+      "\n",
+      "def palindrome_recurs(my_str):\n",
+      "    if len(my_str) < 2:\n",
+      "        return True\n",
+      "    if my_str[0] != my_str[-1]:\n",
+      "        return False\n",
+      "    return palindrome(my_str[1:-1])\n",
+      "\n",
+      "\n",
+      "\n"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [],
+     "prompt_number": 1
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "test_str = \"Go hang a salami. I'm a lasagna hog.\"\n",
+      "\n",
+      "print('case-insensitive functions ignoring punctuation characters')\n",
+      "%timeit palindrome_short(test_str)\n",
+      "%timeit palindrome_regex(test_str)\n",
+      "%timeit palindrome_stringlib(test_str)\n",
+      "\n",
+      "print('\\n\\nfunctions considering all characters (case-sensitive)')\n",
+      "%timeit palindrome_reverse1(test_str)\n",
+      "%timeit palindrome_reverse2(test_str)\n",
+      "%timeit palindrome_recurs(test_str)\n"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "case-insensitive functions ignoring punctuation characters\n",
+        "100000 loops, best of 3: 15.4 \u00b5s per loop"
+       ]
+      },
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "\n",
+        "10000 loops, best of 3: 20.1 \u00b5s per loop"
+       ]
+      },
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "\n",
+        "100000 loops, best of 3: 12.3 \u00b5s per loop"
+       ]
+      },
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "\n",
+        "\n",
+        "\n",
+        "functions considering all characters (case-sensitive)\n",
+        "1000000 loops, best of 3: 500 ns per loop"
+       ]
+      },
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "\n",
+        "100000 loops, best of 3: 2.93 \u00b5s per loop"
+       ]
+      },
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "\n",
+        "1000000 loops, best of 3: 505 ns per loop"
+       ]
+      },
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
\ No newline at end of file
diff --git a/benchmarks/palindrome_timeit.ipynb b/benchmarks/palindrome_timeit.ipynb
index 7893bb2..b6b7c8a 100644
--- a/benchmarks/palindrome_timeit.ipynb
+++ b/benchmarks/palindrome_timeit.ipynb
@@ -1,7 +1,7 @@
 {
  "metadata": {
   "name": "",
-  "signature": "sha256:842cb7ae4f520376ff820e7bcd278db91a026ac1fa159ca6e8a4b38296bc10f5"
+  "signature": "sha256:710150d6bf8fe09c3a2348c765457cdea364ebe260d10f57be9349b32ef3ff50"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -23,6 +23,7 @@
      "input": [
       "import re\n",
       "import timeit\n",
+      "import string\n",
       "\n",
       "# All functions return True if an input string is a palindrome. Else returns False.\n",
       "\n",
@@ -39,6 +40,11 @@
       "def palindrome_regex(my_str):\n",
       "    return re.sub('\\W', '', my_str.lower()) == re.sub('\\W', '', my_str[::-1].lower())\n",
       "\n",
+      "def palindrome_stringlib(my_str):\n",
+      "    LOWERS = set(string.ascii_lowercase)\n",
+      "    letters = [c for c in my_str.lower() if c in LOWERS]\n",
+      "    return letters == letters[::-1]\n",
+      "\n",
       "####\n",
       "#### functions considering all characters (case-sensitive)\n",
       "####\n",
@@ -54,12 +60,15 @@
       "        return True\n",
       "    if my_str[0] != my_str[-1]:\n",
       "        return False\n",
-      "    return palindrome(my_str[1:-1])\n"
+      "    return palindrome(my_str[1:-1])\n",
+      "\n",
+      "\n",
+      "\n"
      ],
      "language": "python",
      "metadata": {},
      "outputs": [],
-     "prompt_number": 6
+     "prompt_number": 1
     },
     {
      "cell_type": "code",
@@ -70,6 +79,7 @@
       "print('case-insensitive functions ignoring punctuation characters')\n",
       "%timeit palindrome_short(test_str)\n",
       "%timeit palindrome_regex(test_str)\n",
+      "%timeit palindrome_stringlib(test_str)\n",
       "\n",
       "print('\\n\\nfunctions considering all characters (case-sensitive)')\n",
       "%timeit palindrome_reverse1(test_str)\n",
@@ -92,7 +102,15 @@
        "stream": "stdout",
        "text": [
         "\n",
-        "10000 loops, best of 3: 20.3 \u00b5s per loop"
+        "10000 loops, best of 3: 20.1 \u00b5s per loop"
+       ]
+      },
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "\n",
+        "100000 loops, best of 3: 12.3 \u00b5s per loop"
        ]
       },
       {
@@ -103,7 +121,7 @@
         "\n",
         "\n",
         "functions considering all characters (case-sensitive)\n",
-        "1000000 loops, best of 3: 508 ns per loop"
+        "1000000 loops, best of 3: 500 ns per loop"
        ]
       },
       {
@@ -111,7 +129,7 @@
        "stream": "stdout",
        "text": [
         "\n",
-        "100000 loops, best of 3: 3 \u00b5s per loop"
+        "100000 loops, best of 3: 2.93 \u00b5s per loop"
        ]
       },
       {
@@ -119,7 +137,7 @@
        "stream": "stdout",
        "text": [
         "\n",
-        "1000000 loops, best of 3: 509 ns per loop"
+        "1000000 loops, best of 3: 505 ns per loop"
        ]
       },
       {
@@ -130,7 +148,7 @@
        ]
       }
      ],
-     "prompt_number": 7
+     "prompt_number": 2
     },
     {
      "cell_type": "code",