What is the [XPath](http://www.w3.org/TR/xpath/) expression to select `<link>` elements with `type="application/rss+xml"` **OR** `type="application/atom+xml"` (RSS and Atom feeds)

* `link[@rel='alternate'][@type='application/rss+xml']` selects RSS feeds
* `link[@rel='alternate'][@type='application/atom+xml']` selects Atom feeds

But what is the single XPath expression for selecting them both?

Thank you.