title: can't click btn-group in Bootstrap row
body: <p><div class="snippet" data-lang="js" data-hide="false" data-console="false" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap.min.css" rel="stylesheet" /&gt;
  &lt;div class="row"&gt;
    &lt;div class="col-md-9"&gt;
      &lt;div class="btn-group pull-left"&gt;
        &lt;a class="btn btn-default" href="/servers"&gt;
  First
  &lt;/a&gt;
        &lt;a class="btn btn-default" href="/servers?page=4"&gt;
  Prev
  &lt;/a&gt;
        &lt;a class="btn btn-default" href="/servers"&gt;
  1
  &lt;/a&gt;
        &lt;a class="btn btn-default" href="/servers?page=2"&gt;
  2
  &lt;/a&gt;
        &lt;a class="btn btn-default" href="/servers?page=3"&gt;
  3
  &lt;/a&gt;
        &lt;a class="btn btn-default" href="/servers?page=4"&gt;
  4
  &lt;/a&gt;
        &lt;a class="btn btn-default disabled"&gt;
  5
  &lt;/a&gt;
        &lt;a class="btn btn-default" href="/servers?page=6"&gt;
  6
  &lt;/a&gt;
        &lt;a class="btn btn-default" href="/servers?page=7"&gt;
  7
  &lt;/a&gt;
        &lt;a class="btn btn-default" href="/servers?page=8"&gt;
  8
  &lt;/a&gt;
        &lt;a class="btn btn-default" href="/servers?page=9"&gt;
  9
  &lt;/a&gt;
        &lt;a class="btn btn-default disabled"&gt;
  …
  &lt;/a&gt;
        &lt;a class="btn btn-default" href="/servers?page=6"&gt;
  Next
  &lt;/a&gt;
        &lt;a class="btn btn-default" href="/servers?page=12"&gt;
  Last
  &lt;/a&gt;
      &lt;/div&gt;
    &lt;/div&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>Source seems like above.
  They are in row class and col-md-9.</p>
  
  <p>When they are full-sized, they are clickable.</p>
  
  <p><img src="https://i.stack.imgur.com/nCzhK.png" alt="enter image description here"></p>
  
  <p>While they are mobile-sized, I can't click some of them.</p>
  
  <p><img src="https://i.stack.imgur.com/jjnQb.png" alt="enter image description here"></p>
  
  <p>I think the reason is row.
  How can I make them to be clickable?</p>