 The Continuation of the Chronicle by Friar George, which was written in the middle of the 10th century, recorded the first historical event – an alliance between the Magyars and the Bulgarians in the late 830s – that can without doubt be connected to the Magyars. The Byzantine Emperor Leo the Wise's Tactics, a book written around 904, contained a detailed description of their military strategies and way of life. Emperor Constantine Porphyrogenitus's De administrando imperio ("On Governing the Empire"), which was completed between 948 and 952, preserves most information on the Magyars'early history. Al-Jayhani, the minister of Nasr II, ruler of the Samanid Empire, collected the reports of merchants who had traveled in the western regions of the Eurasian steppes in the 870s and 880s. Although Al-Jayhani's work was lost, later Muslim scholars Ibn Rusta, Gardizi, Abu Tahir Marwazi, and Al-Bakri used his book, preserving important facts about the late 9th-century Magyars. However, their works also contain interpolations from later periods. Among the sources written in Western Europe, the longer version of the Annals of Salzburg, Regino of Prüm's Chronicon, the Annals of Fulda, and Liutprand of Cremona's Antapodosis ("Retribution"), provide contemporaneous or near-contemporaneous information of the 9th-century Magyars. There are also references to the Magyars dwelling in the Pontic steppes in the legends of Cyril, Methodius and other early Slavic saints. According to historian András Róna-Tas, information preserved in the Russian Primary Chronicle, which was completed in the 1110s, has to be "treated with extreme caution".
