<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<link href="//netdna.bootstrapcdn.com/bootstrap/3.1.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//netdna.bootstrapcdn.com/bootstrap/3.1.0/js/bootstrap.min.js"></script>
<script src="//code.jquery.com/jquery-1.11.1.min.js"></script>
<div class="container">
<div class="row">
<div class="col-md-6">
<div class="panel panel-primary">
<div class="panel-heading">
<h3 class="panel-title">Panel 1</h3>
<span class="pull-right clickable"><i class="glyphicon glyphicon-chevron-down"></i></span>
</div>
<div class="panel-body">Panel content</div>
</div>
</div>
<div class="col-md-6">
<div class="panel panel-success">
<div class="panel-heading">
<h3 class="panel-title">Panel 2</h3>
<span class="pull-right clickable"><i class="glyphicon glyphicon-chevron-up"></i></span>
</div>
<div class="panel-body">Panel content</div>
</div>
</div>
</div>
<div class="row">
<div class="col-md-6">
<div class="panel panel-info">
<div class="panel-heading">
<h3 class="panel-title">Panel 3</h3>
<span class="pull-right clickable"><i class="glyphicon glyphicon-chevron-up"></i></span>