covering natural history, architecture, medicine, geography, geology, and other aspects of the world around him. He stated in the preface that he had compiled 20,000 facts from 2000 works by over 200 authors, and added many others from his own experience. The work was published around AD 77–79, although Pliny probably never finished editing the work before his death in the eruption of Vesuvius in AD 79.[17] Middle Ages Isidore of Seville, one of the greatest scholars of the early Middle Ages, is widely recognized for writing the first encyclopedia of the Middle Ages, the Etymologiae (The Etymologies) or Origines (around 630), in which he compiled a sizable portion of the learning available at his time, both ancient and contemporary. The work has 448 chapters in 20 volumes, and is valuable because of the quotes and fragments of texts by other authors that would have been lost had he not collected them. The most popular encyclopedia of the Carolingian Age was the De universo or De rerum naturis by Rabanus Maurus, written about 830; it was based on Etymologiae.[citation needed] The encyclopedia of Suda, a massive 10th-century Byzantine encyclopedia, had 30 000 entries, many drawing from ancient sources that have since been lost, and often derived from medieval Christian compilers. The text was arranged alphabetically with some slight deviations from common vowel order and place in the Greek alphabet. The early Muslim compilations of knowledge in the Middle Ages included many comprehensive works. Around year 960, the Brethren of Purity of Basra were engaged in their Encyclopedia of the Brethren of Purity.[18] Notable works include Abu Bakr al-Razis encyclopedia of science, the Mutazilite Al-Kindis prolific output of 270 books, and Ibn Sinas medical encyclopedia, which was a standard reference work for centuries. Also notable are works of universal history (or sociology) from Asharites, al-Tabri, al-Masudi, Tabaris History of the Prophets and Kings, Ibn Ru