Today, there are 573 federally-recognized tribes. Many of those tribes use different names to describe themselves, giving us hundreds of tribal names we could use to search for sources.
You can use this technique to search for more than one name at once:
Navajo OR Diné will return results containing either name
Keep in mind that historical events and migrations have divided and combined groups over time, so you often need to make your search time-specific. It's easy to do that in the database America: History & Life, which allows you to put in a range of dates that the article is about in the main search page:
