<p>an <a href="http://example.com">implicit</a> reference link</p>
<p>an <a href="http://example.com">implicit</a> reference link with an empty link definition</p>
<p>an <a href="http://example.com">implicit</a> reference link followed by <a href="http://cnn.com">another</a></p>
<p>an <a href="http://example.com" title="Example">explicit</a> reference link with a title</p>