The works of Oribasius, physician to the Roman emperor Julian, from the 4th century AD, were well known, and were frequently cited in detail by Muhammad ibn Zakariya al-Razi (Rhazes). The works of Philagrius of Epirus, who also lived in the 4th century AD, are only known today from quotations by Arabic authors. The philosopher and physician John the Grammarian, who lived in the 6th century AD was attributed the role of a commentator on the "Summaria Alexandrinorum". This is a compilation of 16 books by Galen, but corrupted by superstitious ideas. The physicians Gessius of Petra and Palladios were equally known to the Arabic physicians as authors of the "Summaria". Rhazes cites the Roman physician Alexander of Tralles (6th century) in order to support his criticism of Galen. The works of Aëtius of Amida were only known in later times, as they were neither cited by Rhazes nor by Ibn al-Nadim, but cited first by Al-Biruni in his "Kitab as-Saidana", and translated by Ibn al-Hammar in the 10th century.