Pythagorean School.
Accounts of Pythagoreanism derive mostly from Aristotle and the Peripatetic School (Aristoxenus, Theophrastus, Eudemus), and from the Neo-Platonists (Porphyry, Iamblichus, Proclus, Simplicius); there are also extracts and references in the compilers (Diogenes Laertius, Stobaeus) and the lexicographers. But these accounts are usually referred to the Pythagorean School in general, not to any particular member. It was a rule that discoveries were referred to Pythagoras himself; and Pythagoras left no writings.