title: Observable.Join example
body: <p>Can someone please provide an example of how to use Observable.Join with two different observable types?<br />
  The best explanation I've <a href="http://www.introtorx.com/uat/content/v1.0.10621.0/17_SequencesOfCoincidence.html#Join" rel="nofollow">found so far here</a> says the left observable opens a window while the right one is for finding a match within this window which makes sense so for. But how is this <code>leftDurationSelector</code> and <code>rightDurationSelector</code> working? The example is just using <code>Publish().RefCount()</code> which I dont understand what it does. For me a duration selector sounds like a time span, e.g. a Buffer window.</p>