https://www.worldhistory.org/protagoras/
Protagoras of Abdera (l. c. 485-415 BCE) is considered the greatest of the Sophists of ancient Greece and the first philosopher in the West to promote...
world history encyclopediaprotagoras
https://www.gutenberg.org/ebooks/subject/18225?sort_order=release_date
Project Gutenberg offers 77,708 free eBooks for Kindle, iPad, Nook, Android, and iPhone.
project gutenbergbooksprotagoras