title: How to include media-breakpoint-up to Bootstrap 4?
body: <p>How to include media-breakpoint-up to Bootstrap 4? </p>
  
  <p>If i am tried:</p>
  
  <pre><code>@include media-breakpoint-up(sm) {
    html {
      font-size: 16px;
    }
  }
  </code></pre>
  
  <p>then I have error:</p>
  
  <p>Error: Undefined mixin 'media-breakpoint-up'.  on line 14.......</p>
  
  <p>I use Bootstrap 4 by includes files:</p>
  
  <pre><code>&lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/3.0.0/jquery.min.js" integrity="sha384-THPy051/pYDQGanwU6poAc/hOdQxjnOEXzbT+OuUAFqNqFjL+4IGLBgCJC3ZOShY" crossorigin="anonymous"&gt;&lt;/script&gt;
      &lt;script src="https://cdnjs.cloudflare.com/ajax/libs/tether/1.2.0/js/tether.min.js" integrity="sha384-Plbmg8JY28KFelvJVai01l8WyZzrYWG825m+cZ0eDDS1f7d/js6ikvy1+X+guPIB" crossorigin="anonymous"&gt;&lt;/script&gt;
  &lt;script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.4/js/bootstrap.min.js" integrity="VjEeINv9OSwtWFLAtmc4JCtEJXXBub00gtSnszmspDLCtC0I4z4nqz7rEFbIZLLU" crossorigin="anonymous"&gt;&lt;/script&gt;
  </code></pre>