From the OAIster website:
"OAIster is a union catalog of digital resources." It also says that OCLC and the University of Michigan are collaborating (as of January 2009).Since the project was launched in 2002, this may be old news to many.
Using "Backus" as my search term for the entire record field (can be narrowed by author, title, etc) and all types of records (text, pictures, etc) there were 863 hits. Many duplicates, but a couple of gems surfaced.