diff --git a/README.md b/README.md
index 73c8e7e..a7043bd 100644
--- a/README.md
+++ b/README.md
@@ -105,7 +105,7 @@ $ luarocks install argparse
 
 #### Problems with old luarocks versions
 
-You may get an error like `Parse error processing dependency '30log >= 0.8'` if you use luarocks 2.1 or older. In this case, either upgrade to at least luarocks 2.1.1 or install [30log](http://yonaba.github.io/30log/) manually, then download the rockspec for argparse, remove the line `"30log >= 0.8"` and run
+You may get an error like `Parse error processing dependency '30log >= 0.9.1'` if you use luarocks 2.1 or older. In this case, either upgrade to at least luarocks 2.1.1 or install [30log](http://yonaba.github.io/30log/) manually, then download the rockspec for argparse, remove the line `"30log >= 0.9.1"` and run
 
 ```bash
 $ luarocks install /path/to/argparse/rockspec
diff --git a/doc/index.html b/doc/index.html
index e1d89a3..15e0b07 100644
--- a/doc/index.html
+++ b/doc/index.html
@@ -55,6 +55,8 @@ <h2 id="project_tagline"></h2>
 <li><a href="#setting-number-of-invocations">Setting number of invocations</a></li>
 </ul>
 </li>
+<li><a href="#mutually-exclusive-groups">Mutually exclusive groups</a></li>
+
 <li>
 <a href="#commands">Commands</a>
 
@@ -408,6 +410,27 @@ <h3>
 <pre><code>verbosity   2
 </code></pre>
 
+<h2>
+<a name="mutually-exclusive-groups" class="anchor" href="#mutually-exclusive-groups"><span class="octicon octicon-link"></span></a>Mutually exclusive groups</h2>
+
+<p>A group of options can be marked as mutually exclusive using <code>:mutex()</code> method of the Parser class. </p>
+
+<div class="highlight highlight-lua"><pre><span class="n">parser</span><span class="p">:</span><span class="n">mutex</span><span class="p">(</span>
+   <span class="n">parser</span><span class="p">:</span><span class="n">flag</span> <span class="s2">"</span><span class="s">-q"</span> <span class="s2">"</span><span class="s">--quiet"</span><span class="p">,</span>
+   <span class="n">parser</span><span class="p">:</span><span class="n">flag</span> <span class="s2">"</span><span class="s">-v"</span> <span class="s2">"</span><span class="s">--verbose"</span>
+<span class="p">)</span>
+</pre></div>
+
+<p>If more than one element of a mutually exclusive group is used, an error is raised. </p>
+
+<div class="highlight highlight-bash"><pre><span class="nv">$ </span>lua script.lua -qv
+</pre></div>
+
+<pre><code>Usage: script.lua ([-q] | [-v]) [-h]
+
+Error: option '-v' can not be used together with option '-q'
+</code></pre>
+
 <h2>
 <a name="commands" class="anchor" href="#commands"><span class="octicon octicon-link"></span></a>Commands</h2>
 
diff --git a/rockspecs/argparse-0.2.0-1.rockspec b/rockspecs/argparse-0.2.0-1.rockspec
new file mode 100644
index 0000000..1185036
--- /dev/null
+++ b/rockspecs/argparse-0.2.0-1.rockspec
@@ -0,0 +1,23 @@
+package = "argparse"
+version = "0.2.0-1"
+source = {
+   url = "git://github.com/mpeterv/argparse.git",
+   tag = "0.2.0"
+}
+description = {
+   summary = "A feature-rich command-line argument parser",
+   detailed = "argparse supports positional arguments, options, flags, optional arguments, subcommands and more. argparse automatically generates usage, help and error messages. ",
+   homepage = "https://github.com/mpeterv/argparse",
+   license = "MIT/X11"
+}
+dependencies = {
+   "lua >= 5.1, < 5.3",
+   "30log >= 0.9.1"
+}
+build = {
+   type = "builtin",
+   modules = {
+      argparse = "src/argparse.lua"
+   },
+   copy_directories = {"doc", "spec"}
+}