inks use a second set of square brackets, inside
which you place a label of your choosing to identify the link:</p>

<pre><code>This is [an example][id] reference-style link.
</code></pre>

<p>You can optionally use a space to separate the sets of brackets:</p>

<pre><code>This is [an example] [id] reference-style link.
</code></pre>

<p>Then, anywhere in the document, you define your link label like this,
on a line by itself:</p>

<pre><code>[id]: http://example.com/  &quot;Optional Title Here&quot;
</code