The Beethoven-Haus Bonn is one of the two most important archives of primary source documents concerning composer Ludwig van Beethoven and contains unique collections of the Beethoven-Haus music manuscripts, first editions, letters, and pictures.
The digitized versions of Wolfgang Amadeus Mozart's musical compositions with the musical text and the critical commentaries of the entire Neue Mozart-Ausgabe, edited by the Internationale Stiftung Mozart.
Authoritative, detailed, multilingual descriptions of digital images, texts, video clips, sound recordings, and complex media objects related to the performing arts around the world, plus information about related pieces, productions, performers, and works.
Encyclopedia Britannica - includes web sites, periodical articles, related books – free version provides only a few paragraphs of information from the concise encyclopedia