This is a very interesting question. When searching eNotes for American Indians, there are a number of study guides offered in more specific areas, such as "American Indian Women" and "American Indian Theater." Refining your search to include "History" provides a timeline for American Indians.

However, as we use the English language (which provides limitless ways in which to share a single piece of information or a thought), we find that the language is as alive as those who use it: it is always changing. It also reflects slang, for instance. Slang is defined as...

...very informal usage in vocabulary and idiom that is characteristically more metaphorical, playful, elliptical, vivid, and ephemeral than ordinary language, as Hit the road.

These changes make it difficult for non-native English speakers to understand it, often times because of slang or idioms; and even generations struggle to understand each other, as each generation seems to have its own slang. Words from other languages are adapted into English as well. In addition, language and social awareness also have had a strong impact on our language. For example, for many years "American Indian" was used to be more politically correct than calling members of this race simply "Indians." With the large number of immigrants the U.S. sees every year, there soon developed a need to differentiate between people from India and those native to America—descended from the tribes that inhabited North America long before European settlers arrived.

So to be politically correct, it shows a clear specificity—as well as greater respect to these Americans who are trying to hold on to their culture with dignity and recognition of the richness of their heritage—by referring to this race as Native Americans.

If you search under this title, you will find an even longer list of sources as your disposal. See the link below as a beginning.

At the same time, Native American... 

...also includes Hawaiians and some Alaskan natives not considered American Indians. When referred to in general, American Indians often prefer to be called by their tribal names, such as Nez Perce, Navajo, Sioux, or Oneida.

Searching for tribal history and information will also provide a new store of information for you.