The nucleus of the stories is formed by a Pahlavi Sassanid Persian BOOK called HazārAfsānah ("Thousand Myths", in Persian:هزارافسانه), a collection of ancient Indian and Persian folk tales. During the reign of the Abbasid Caliph Harun al-Rashid in the 8th centuryC.E., Baghdad had become an important cosmopolitan city. Merchants from Persia, China, India, Africa, and Europe were all found in Baghdad. It was during this time that many of the stories, which were originally folk stories transmitted orally, are thought to have been collected and later compiled into a single BOOK . The later compiler and translator into Arabic is reputedly storyteller Abu abd-Allah Muhammed el-Gahshigar in the ninth century C.E. The frame story of Shahrzad seems to have been added in the fourteenth century. The first modern Arabic compilation was published in Cairo in 1835.