PayPal logo provided by PayPal Logo Centre: https://www.paypal.com/uk/webapps/mpp/logo-center
Background image provided in the assets directory under Creative Commons licence (CC):
Find out more at: https://creativecommons.org/licenses/
Favico created using Font Awesome, under OFL licence: http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=OFL
Example images of books are fetched using REST API created and shared by Open Library.
Find out more at: https://openlibrary.org/dev/docs/api/covers