The primary source for the Greco-Persian Wars is the Greek historian Herodotus.

Entity and relation annotations:
id: 0
type: entity
value: text: the Greco-Persian Wars
labels: <Event>
id: 1
type: entity
value: text: Herodotus
labels: <Person>
id: 2
type: entity
value: text: the Greek historian
labels: <Title>
type: relation
to_id: 2
labels: Person:holds_title:Title
from_id: 1
type: relation
to_id: 0
labels: Person:participates_in:Event
from_id: 1