Censorinus, De die natali 5.4. N. Sallman (Censorini de die natali liber [Leipzig: Teubner, 1983] 8 ad loc.) gives the pertinent references to the fragments of the authors mentioned, as does R. Rocca-Serra, in Censorinus: Le jour natal (Paris: Vrin, 1980), p. 45 (his French translation is on p. 8). In 6.5 and 6.8 Censorinus discusses Parmenides’ and Anaxagoras’ ideas on the role of female semen.