Question: Byzantium, Chalcedon, Heraclea Pontica and Tium formed what league?
Sentence: Other city states formed federated states in self-defense, such as the Aetolian League (est. 370 BCE), the Achaean League (est. 280 BCE), the Boeotian league, the "Northern League" (Byzantium, Chalcedon, Heraclea Pontica and Tium) and the "Nesiotic League" of the Cyclades.
Answer in sentence: yes