Tolong jelaskan mengenai Sumber dari Philopoimon

Polybios' Histories (x–xxiii) is the chief authority on the life of Philopoemen. These and a special treatise on Philopoemen (now lost) were used by Plutarch "Philopoemen", Pausanias (viii. 49SI), Livy (xxxi–xxxviii), and indirectly by Justin (xxx–xxxiv).