Find In-Depth Articles

Sometimes you want to find more about a topic and you find a lot of superficial news articles and blog posts that keep rehashing the same information. Google shows a list of in-depth articles for some queries, but this feature seems to be restricted to the US and it's only displayed for some queries.

How to manually trigger Google's in-depth section? Just add &tbs=ida:1&gl=us to a Google search URL and you'll see a list of 10 in-depth articles from sites like Wall Street Journal, New York Times‎, Wired, New Yorker, Slate and more. Some examples: [Google], [Daft Punk], [robots], [Russia], [happy].