In the United States, many archives and special collection repository writing finding aids to aid users in finding materials in their collections. The links provide access to different interfaces designed to provide users with the chance to cross search those aids for finding material.
For information on how to read a finding aid, check out
You can also search in Google for ([FOCUS] "finding aid") with your [FOCUS] being the name of the author or topic you're searching. For example (Yoshiko Uchida "finding aid") in a Google search should lead you to Bancroft's aid for the Yoshiko Uchida papers 1903-1994 online (direct link).
