By admin | 2:20 PM PDT, Sat October 09, 2021 Credits The image in the Question is from NASA website. It is a government document, and not eligible for copyright. The image in the Explanation is from the Mathematical Association of America (MAA) website. https://www.maa.org/press/periodicals/convergence/eratosthenes-and-the-mystery-of-the-stades-eratosthenes-argument