History of the Peloponnesian War

Nymphodorus, when he came to Athens, made this league between them and Sitalces and caused Sadocus the son of Sitalces to be made free of Athens and also undertook to end the war in Thrace. For he would persuade Sitalces to send unto the Athenians a Thracian army of horsemen and targeteers.

He likewise reconciled Perdiccas to the Athenians, and procured of him the restitution of Therme. And Perdiccas presently aided the Athenians and Phormio in the war against the Chalcideans.

Thus were Sitalces the son of Teres, king of Thrace, and Perdiccas the son of Alexander, king of Macedonia, made confederates with the Athenians.