Sempiternus Rex Christus §13

¹³ Nevertheless, at the emperor's wish and with the pope's approval, a council was held. Chalcedon was a city of Bithynia near the Thracian Bosphorus, within sight of Constantinople, which was situated on the opposite bank. Here, in the vast suburban basilica of St. Euphemia, virgin and martyr, on the 8th of October, assembled the fathers, who had previously met for this purpose in the city of Nicea. They were about 600 in number, all of the East, except for two exiles from Africa.