title: Yammer Dev Documentation for possible reference return types?
body: <p>when getting back references from Yammer through the dev api, they can be of a few different types. Is there any documentation somewhere that describes the JSON model of returned objects?</p>
  
  <p>Right now I have got the following from just reading the returned JSON.</p>
  
  <pre><code>Type:
  - "user"
  - "guide"
  - "group"
  - "thread"
  - "topic"
  </code></pre>
  
  <p>But there could be other types I'm not expecting which could be sent in the future. Is there a list somewhere that describes indepth all the possible return types from the Yammer API?</p>