Once Upon a Fic Exchange

Daphne and Phoebus (I put Phoebus in Greek and Roman Mythology to match up with Daphne) - Metamorphoses, Book 1, Ovid. http://www.theoi.com/Text/OvidMetamorphoses1.html (I like this source because it is easy to read (big print for the win!) and to search)

Pythia (Hellenistic Religion and Lore) - the AO3 fandom tag she comes up in is Greek and Roman Mythology - her Wikipedia page is by far the most complete source of information about the Oracle and is extensively foot-noted. https://en.wikipedia.org/wiki/Pythia

If you want specific sources for the two Shakespeare plays, I can list them, too. But I have no preference. Thank you for letting me include them.