it's a reference link (as documented at http://daringfireball.net/projects/markdown/syntax). The syntax should be totally correct so long as dgeni understands them

> Here’s an example of reference links in action:
>
>I get 10 times more traffic from [Google] [1] than from
>[Yahoo] [2] or [MSN] [3].
>
>  [1]: http://google.com/        "Google"
>  [2]: http://search.yahoo.com/  "Yahoo Search"
>  [3]: http://search.msn.com/    "MSN Search"