The Internet Archive acquires most materials from donations, such as hundreds of thousands of 78 rpm discs from Boston Public Library in 2017, a donation of 250,000 books from Trent University in 2018, and the entire collection of Marygrove College's library in 2020 after it closed. All material is then digitized and retained in digital storage, while a digital copy is returned to the original holder and the Internet Archive's copy, if not in the public domain, is borrowed to patrons worldwide one at a time under the controlled digital lending (CDL) theory of the first-sale doctrine.