The Authors Guild is appealing a US judge's decision in a long-running case that cleared legal obstacles for Google's massive book-scanning project, court documents showed Monday.

The group filed a notice of appeal in the case following a November 14 ruling by Federal Judge Denny Chin.

Arguments are to be filed at a later date with the Second Circuit Court of Appeals in New York.

The guild vowed to appeal the case after Chin ruled that Google's project is "fair use" under copyright law because it provides vital educational and other public benefits.

The case, which dates back to 2005, centers on a Google program started in 2004 to create an electronic database of books that could be searchable by keywords.

Google has scanned more than 20 million books so far in the project. Books in the public domain -- without current copyrights -- are made available online to the public for free. For copyrighted books, Google offers a searchable database that displays snippets of text.

Google has long argued that its program is in compliance with copyright law and acts like a "card catalog for the digital age."