Where are their scanning centers? The link (http://www.archive.org/scanning http://www.archive.org/scanning) said they have lots of them, but doesn't describe w

Where are their scanning centers? The link (http://www.archive.org/scanning http://www.archive.org/scanning) said they have lots of them, but doesn't describe where. I assume I can't just show up and expect to get my books scanned, so I'd be interested to understand the process better. Can an individual participate or are they only working with their partners?