Annas, Julia. Ancient Philosophy: A Very Short Introduction. Oxford, UK: Oxford University Press, 2000. Intended audience: general public, undergraduate.
Burkert, Walter. Lore and Science in Ancient Pythagoreanism. Trans. by Edwin L. Minar, Jr. Cambridge, MA, USA: Harvard University Press, 1972. Intended audience: undergraduate, graduate/professional.
Kahn, Charles H. Pythagoras and the Pythagoreans: A Brief History. Indianapolis, IN, USA: Hackett, 2001. Intended audience: general public, undergraduate, graduate/professional.
Kirk, G.S., Raven, J.E., & Schofield, M. The Presocratic Philosophers (2nd ed.). Cambridge, UK: Cambridge University Press, 1983. Intended audience: undergraduate, graduate/professional.
Papers
O’Meara, Dominic J. Pythagoras revived: Mathematics and philosophy in late antiquity. 1990. doi: 10.1093/0198239130.001.0001
Fletcher, Colin R. Thales: Our founder? 1982. doi: 10.2307/3615512
Aaboe, A. Scientific astronomy in antiquity. 1974. doi: 10.1098/rsta.1974.0007
Buck, R. Creighton. Sherlock Holmes in Babylon. 1980. doi: 10.2307/2321200
Robson, Eleanor. Words and pictures: New light on Plimpton 322. 2002. doi: 10.2307/2695324