How do I create a recipe for content with these attributes

Hello -

I've been messing around with recipes but haven't yet been able to get a clean result. For my news site content I notice that unwanted content uses a particular article tag and wanted another. For example:

<article class="asset clearfix">
...
...
...
</article>


<article class="asset story clearfix">
...
...
...
</article>

The former class includes photo galleries and video stories which I don't want any content from. The latter is news stories.

What do i need to do in my recipes to ignore all pages with the former content and only include the latter "asset story clearfix"?

Thanks