Among these sources are: "Destan-ı Tevarih-i Al-i Osman" (the oral history of the Ottomans), written in the 14th century by the Ottoman poet and court physician better known as Ahmedî (1334-1413 CE), ' (the joy of histories) by Şükrullah (d. 1464 CE), and ' (history of the Ottomans) by Derviş Ahmed Âşıkî, known as Âşıkpaşazâde (1400–1484 CE). ِAdditionally, these remaining sources are not the originals, but rather copies, or copies of the copies that were rewritten over the years, leading to a probable loss or altering in the information. In fact, it is accepted that Ottoman, European, and Byzantine sources are not very reliable when considering the origins of Osman and his clan. On one hand, the oldest known records originally written by the Ottomans all date back to the period that followed the conquest of Constantinople (1453 CE). On the other hand, none of the Byzantine historians did refer in their writings to the origin of the Ottomans. As for European historians, these Turkic Muslim peoples were out of their interests. However, that changed after a century of this period, when the Ottomans began to pose a threat to Europe. Ottoman historian Kemalpaşazâde mentioned that Osman was Ertuğrul's youngest son and that he was raised in the traditional nomadic Turkic ways: he learned wrestling, swordsmanship, horse riding, arrow shooting, and falconry, from an early age. He quickly mastered the previously mentioned skills outperforming all his brothers. He was also taught the principles of Islam, and was influenced by the teachings of Sufi sheikhs, mostly his mentor Sheikh Edebali, and this was reflected in his personality and lifestyle.