National Academic Press
https://notes.nap.edu/

UCL Press
https://uclpress.co.uk/

Librivox
https://librivox.org/

University of Michigan Press Ebooks
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• Project Gutenberg is a library of over 75,000 free eBooks
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Library of Congress.
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• OpenStax is an educational initiative headed by Rice
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SpringerOpen open access books
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