bootstrap 4 glyphicons not showing code example

Example 1: bootstrap glyphicons

<link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap-glyphicons.css">

Example 2: glyphicon-user bootstrap 4

<button type="button" class="btn btn-default navbar-btn">Sign in</button>

Example 3: glyphicons in bootstrap 4

<div class="panel panel-primary">...</div>
<div class="panel panel-success">...</div>
<div class="panel panel-info">...</div>
<div class="panel panel-warning">...</div>
<div class="panel panel-danger">...</div>