1. BOWKER Homepage. https://www.bowker.com/en/products-services/bowker-book-data/. Accessed 21 May 2022
2. UNESCO Homepage. http://uis.unesco.org. Accessed 21 May 2022
3. GUINESS BOOK OF RECORDS Homepage. https://www.guinnessworldrecords.com/world-records/best-selling-book-of-non-fiction. Accessed 11 June 2022
4. BIBLE Homepage. https://www.bible.com/sk/versions. Accessed 11 June 2022
5. WORLD ATLAS Homepage. https://www.worldatlas.com/articles/best-selling-books.html. Accessed 12 June 2022