Missing documentation for using references in Docs

I am in the process of switching over from Doctrine 2.0.7 to Doctrine 2.1 and one of the major missing components in my entities was the new use of using the mapping entity.

Example:

 
<?php
namespace My\Project\Entities;
use Doctrine\ORM\Mapping\Entity as ORM;
/**
 * @ORM\Entity(...)
 */
class Something
{
// Doctrine annotations here
}

The nessecity for this to be included in the entities is (as far as I can tell) nowhere to be found in the docs, so I am a little curious as to how people are supposed to know. I have also had a look here: http://www.doctrine-project.org/blog/doctrine-2-1-beta-release and can see no references too it.

Am I missing something; or is it really just missing from the docs?