Around 1450, Bessarion began to place his ecclesiastical coat of arms on his books and assign shelf marks, an indication that the collection was no longer limited to personal consultation but that he intended to create a lasting library for scholars. In 1454, following the fall of Constantinople to the Ottoman Turks (1453) and the ensuing devastation, he charged Michael Apostolius and Theophanes, bishop of Athens, with the task of locating and purchasing specific works throughout Greece, primarily in Adrianople, Athens, Thessaloniki, Aenos, Gallipoli, and Constantinople, with the objective of preserving the writings of the classical Greek authors and the literature of Byzantium. He also established a "scriptorium" on Crete, under the direction of Apostolius, where hired scribes copied the texts that could not be found for purchase. A similar "scriptorium" existed in his Roman residence where other texts were copied. Many of the originals were borrowed for this purpose from the monastery of Santa Croce di Fonte Avellana (Marche) and from several Basilian monasteries in southern Italy, of which Bessarion was nominated protector and apostolic visitor in 1446. These included his discoveries of the "Posthomerica" by Quintus Smyrnaeus and the "Abduction of Helen" by Coluthus, which would have otherwise been lost as a result of the Ottoman invasion of Otranto and the destruction of the monastic library of (Apulia) in 1480. Copies of Augustine's complete works were commissioned from the bookseller Vespasiano da Bisticci.