Herodotus Book 7: Polymnia, 222 "Thespians very willingly, for they said that they would not depart and leave Leonidas and those with him, but they stayed behind and died with them."
Herodotus Book 8: Urania, 50 "For the army which directed its march through Boeotia in company with Xerxes, after it had burnt the city of the Thespians (the inhabitants having left it and gone to the Peloponnese)..."
Herodotus Book 9: Calliope, 30 "...and with the Thespians who were present the number of eleven myriads was fully made up; for there were present also in the army those of the Thespians who survived, being in number about one thousand eight hundred, and these too were without heavy arms."
theoi.com
Pausanias Book 10 Phocis, 20.2 "...if we except the Lacedaemonians, Thespians and Mycenaeans, the rest left the field before the conclusion of the fighting."
