Eusebius, Ecclesiastical History, Volume 2:

Books 6-10 of Eusebius' History begin with the life of Origen late 2nd century and extend through the victories of Constantine. Eusebius records the movement of the Gospel to the Roman world, persecutions under Emperors, successions of bishops in various churches, controversies in the Church, heretics and arguments against them, the histories of individual church leaders, etc. Greek, with English translation on opposite facing pages and critical notes. Eusebius of Caesarea (c. 260-c. 340) was bishop of Caesarea and a principal participant in the controversies regarding the relationships of the three persons of the Trinity prior to and following the council of Nicaea.