English literature retrieval websites include forgotten books, Gutenberg Project, World Public Library, Social Science Research Network, Open Access Library, Blackwell Electronic Journals, OA resources of Scientific Research Press, Electronic Journals of HighWire Press, Free Books and JustFreeBooks.

WitGuides, many books, free e-books, Bioline International, Internet Archive, free e-books, digital book index, economic thought history stack of McMaster University, international and regional digital collection of California University.

ProQuest

ProQuest is a full-text retrieval system for doctoral dissertations, and the full name of PQDD is ProQuest Digital Dissertation. ProQuest's parent company is UMI, Answer Company. UMI, founded in 1938, is one of the largest information storage and publishers in the world.

He is also a famous publisher in American academic circles. Providing information services to more than 160 countries in the world, covering business management, social sciences, humanities, news, science and technology, medicine, finance, taxation and other fields.