Atiya published a large study entitled
The Crusades in the Later Middle Ages in 1938, and was also the first author of
The Coptic Encyclopedia, published in 1991. The chapters on the Copts in his book
The History of Eastern Christianity (1968, 1980) have become landmarks, not only for specialists but also for the general public. He could speak English, Arabic, French, German, Italian, Latin, and to a lesser extent, Spanish, Greek, Coptic, Turkish, Welsh, and Dutch. ==Academic career==