For those of you who wish to travel abroad, do research on foreign relations or just interested in history, this link to the State Department’s Treaties in Force should be of great help to you. It is broken down into subject matter and has helpful references at the beginning of the document.
The Legal and Court History of Cochise County collection in the Arizona Memory Project contains digitized copies of the testimonies of witnesses to the shootout at the O.K. Corral. See the full list of documents here.