Ludwig Ritter von Köchel since undergone revisions. Mozart's works are often referred to by their K-numbers ("cf." opus number); for example, the "Jupiter" symphony, "Symphony No. 41" K. 551. Moreover, Köchel arranged Mozart's works into twenty-four categories, which were used by Breitkopf & Härtel when they published the first complete edition of Mozart's works from 1877 to 1910, a venture partly funded by Köchel. He also catalogued the works of Johann Fux. Ludwig Ritter von Köchel Ludwig Alois Friedrich Ritter von Köchel (; 14 January 1800 – 3 June 1877) was an Austrian musicologist, writer, composer, botanist and publisher. He is best known for
Catalogues of Beethoven compositions and Hans Halm published a catalogue of Beethoven's works, in which they assigned numbers to 205 "Werke ohne Opuszahl" (meaning "works without opus number" in German) to "some" of Beethoven's unpublished works. These numbers given these works are generally preceded by "WoO". The Kinsky–Halm catalogue also lists 18 works in an appendix as being either doubtfully attributed, or simply spurious. Some of those listed as doubtful have since been shown to be authored by Beethoven. These numbers are generally preceded by "Anh.", short for German "Anhang", meaning "appendix". The Swiss composer and musicologist Willy Hess also researched and published a