(1) A link under the 3 in-depth articles to show more in-depth articles
(2) Explore links to other topics and queries that will show more search results that contain in-depth articles.
Here is a picture of a search for [federal reserve] that shows these two features:
Rubén Gómez documented how to search Google' in-depth articles with a URL parameter addition. Specifically adding &ida_m=1 to the end of your search URL.
For more on how to get your content to show up in these results, see our original story on in-depth articles.
Forum discussion at Google+.