Google adds a library catalog search

Google Book Search now links to a library catalog search to help users find a brick-and-morter library that owns the book. Look at the bottom of Google's return page for the link.

Most of the examples I tried used WorldCat but not all do. In the Google blog post announcing the new feature, Google says "we have worked with more than 15 library union catalogs that have information about libraries from more than 30 countries, as well as with our colleagues working on Google Scholar (which includes a similar feature just for scholarly books)."

Update. Run a number of Google book searches and you'll notice that some do and some don't provide a link to a library catalog search. Over at ResourceShelf, Gary Price has a handful of examples. His verdict so far: "Hard to find a pattern."