Even the latter offered instruction in the ancient classics, and included literary, philosophical, and scientific texts in its curriculum. The monastic schools concentrated upon the Bible, theology, and liturgy. Therefore, the monastic scriptoria expended most of their efforts upon the transcription of ecclesiastical manuscripts, while ancient-pagan literature was transcribed, summarized, excerpted, and annotated by laymen or clergy like Photios, Arethas of Caesarea, Eustathius of Thessalonica, and Basilius Bessarion. Byzantine scientists preserved and continued the legacy of the great Ancient Greek mathematicians and put mathematics in practice. In early Byzantium (5th to 7th century) the architects and mathematicians Isidore of Miletus and Anthemius of Tralles used complex mathematical formulas to construct the great Hagia Sophia church, a technological breakthrough for its time and for centuries afterwards due to its striking geometry, bold design and height. In late Byzantium (9th to 12th century) mathematicians like Michael Psellos considered mathematics as a way to interpret the world. Middle Eastern Christians especially the adherents of the Church of the East (Nestorians), contributed to the Arab Islamic Civilization during the Ummayad and the Abbasid periods by translating works of Greek philosophers to Syriac and afterwards to Arabic. During the 4th through the 7th centuries, scholarly work in the Syriac and Greek languages was either newly initiated, or carried on from the Hellenistic period. Centers of learning and of transmission of classical wisdom included colleges such as the School of Nisibis, and later the School of Edessa, and the renowned hospital and medical academy of Jundishapur; libraries included the Library of Alexandria and the Imperial Library of Constantinople; other centers of translation and learning functioned at Merv, Salonika, Nishapur and Ctesiphon, situated just south of what later became Baghdad. Many scholars of the House of Wisdom were of Christian background; the House of Wisdom was a library, translation institute, and academy established in Abbasid-era Baghdad, Iraq. Nestorians played a prominent role in the formation of Arab culture, with the Jundishapur school being prominent in the late Sassanid, Umayyad and early Abbasid periods. Notably, eight generations of the Nestorian Bukhtishu family served as private doctors to caliphs and sultans between the 8th and 11th centuries. The migration waves of Byzantine scholars and émigrés in the period following the Crusader sacking of Constantinople in 1204 and the end of the Byzantine Empire in 1453, is considered by many scholars key to the revival of Greek and Roman studies