Orientalis Ecclesiae §17

¹⁷ Let Cyril of Alexandria be a model to all in the energy and fortitude with which he defended the faith and kept it inviolate. No sooner did he discover the error of Nestorius than he wrote letters and other works in refutation of it, appealed to the Roman Pontiff and, acting in his name at the Council of Ephesus, crushed and condemned the growing heresy with admirable learning and unflinching courage. The result was that, when Cyril's 'dogmatic' letter had been publicly read, all the Fathers of the Council acclaimed it by solemn verdict as being in complete accordance with the true faith.