Type some outrageous stuff in the box and see what happens. Try a book title, journal article title, author name. The single search box may give you what you're looking for and it's a simple place to start. Check out "Refining Your Search" for some ideas on how to filter and scope your search after you get results. "Search Tips" will show you some more advanced techniques.
Books, media items, and anything else physically located in the library.
Everything Antioch University has available, including digital items.
All the things. Everywhere.