The principal sources for the early Sasanian period are not contemporary. Among them the most important are the Greeks Agathias and Malalas, the Persian Muslims al-Tabari and Ferdowsi, the Armenian Agathangelos, and the Syriac "Chronicles" of "Edessa" and "Arbela", most of whom depended on late Sasanian sources, especially "Khwaday-Namag". The "Augustan History" is neither contemporary nor reliable, but it is the chief narrative source for Severus and Carus. The trilingual (Middle Persian, Parthian, Greek) inscriptions of Shapur are primary sources. These were isolated attempts at approaching written historiography however, and by the end of the 4th century AD, even the practice of carving rock reliefs and leaving short inscriptions was abandoned by the Sasanians.