Such as Kremsmünster Abbey for example, boasting a library that contains valuable volumes and art treasures; among them the world-famous "Codex Millenarius" manuscript. In medieval times the most famous writer of Austrian literature was the Upper Austrian minstrel Dietmar von Aist. In 1501 a performance of Conrad Celtis´play "Ludus Dianae" was very well-received. The most famous Austrian Baroque writers were Johann Beer and Simon Rettenpacher. The age of the great Upper Austrian writers began in the 19th century with Franz Stelzhammer, a dialect poet, and Adalbert Stifter, a member of the late classical period. In more recent years writers like Thomas Bernhard and Gertraud Fussenegger strongly influenced German and Austrian literature.