Google on Wednesday started offering free downloads of out-of-copyright books from its library partners, which include Harvard, the New York Public Library and the University of California.

The complete work of such classics as Dante's "Inferno" and Isaac Newton's "Principia" are available in PDF format through Google Book Search.

Out-of-copyright books have been available for reading online through Book Search. The new feature, however, makes it possible for people to store books on their computers and make copies. The available public domain books include both well-known classics and lesser-known scholarly works.

Sidney Verba, director of the Harvard University Library, said Google's initiative to digitize library collections opens up a treasure chest of information on historical events, places of interest and matters cultural or scientific that was previously difficult for most people to find.

"What has been tucked away in large research library collections and available only to a few, can now be discovered and read by people everywhere," Verba said in a joint statement with Google.

While library partners praise Google's efforts, writers and publishers have been less enthusiastic. The initiative also includes digitizing copyrighted books that are made available in the form of text snippets around search terms.

Google argues the practice is legal under the fair-use exemption, but copyright holders say the Mountain View, Calif., search engine does not have the right to store their property in its database without their permission. The Authors Guild and the Association of American Publishers have filed separate lawsuits against Google.

Nevertheless, Google said Wednesday it remains committed to promoting "the discovery of the world's books, whether rare, common, popular or obscure." Analysts say the initiative also provides a new arena for Google to someday target with search-related advertising.

To find books to download, visitors need to select the "full view" button when using Book Search, and then click on the "download" button. Besides Stanford, Harvard and U.C., Oxford, the University of Michigan and the New York Public Library have also opened their collections.