title: Cannot find module 'rxjs/subject/BehaviorSubject'
body: <p>I am using Angular 2.</p>
  
  <p>When I use either of these two, my program runs well:</p>
  
  <pre><code>import { BehaviorSubject } from 'rxjs/Rx';
  import { BehaviorSubject } from 'rxjs';
  </code></pre>
  
  <p>However, I try to use the following way:</p>
  
  <pre><code>import { BehaviorSubject } from 'rxjs/subject/BehaviorSubject';
  </code></pre>
  
  <p>But I failed, my browser console shows:</p>
  
  <blockquote>
    <p>Uncaught Error: Cannot find module 'rxjs/subject/BehaviorSubject'</p>
  </blockquote>
  
  <p>How can I use third way correctly? Thanks</p>