title: LESS - how to refer bootstrap css classes in less?
body: <p>I want to refer multiple css classes in one less class but I keep getting following error, any idea what I maybe doing wrong here? 
  I newbie to LESS, so if there is any better option to achieve this, I would be happy to try it out as well.</p>
  
  <pre><code>NameError: .btn is undefined
  in qx.less on line 2, column 2:
  </code></pre>
  
  <p>Here is my setup</p>
  
  <pre><code>&lt;link rel='stylesheet'         href='/webjars/bootstrap/3.1.1/css/bootstrap.min.css'&gt;
  &lt;link rel="stylesheet/less"    href='/assets/less/qx.less'&gt;
  &lt;script type='text/javascript' src='/webjars/less/1.7.0/less.min.js'&gt;&lt;/script&gt;
  </code></pre>
  
  <p>Content of qx.less - here I am trying to create qx-button which combines .btn and .btn-success of bootstrap.</p>
  
  <pre><code>#qx-button {
      .btn;
      .btn-success;
  }
  </code></pre>