In addition to procuring books from libraries, Google also obtains books from its publisher partners, through the "Partner Program" – designed to help publishers and authors promote their books. Publishers and authors submit either a digital copy of their book in EPUB or PDF format, or a print copy to Google, which is made available on Google Books for preview. The publisher can control the percentage of the book available for preview, with the minimum being 20%. They can also choose to make the book fully viewable, and even allow users to download a PDF copy. Books can also be made available for sale on Google Play. Unlike the Library Project, this does not raise any copyright concerns as it is conducted pursuant to an agreement with the publisher. The publisher can choose to withdraw from the agreement at any time.