Busoni gave many of his works opus numbers; some numbers apply to more than one work (after the composer dropped some of his earlier works from his acknowledged corpus). Furthermore, not all the composer's numbers are in temporal order. The musicologist Jürgen Kindermann has prepared a thematic catalogue of his works and transcriptions which is also used, in the form of the letters BV (for "Busoni Verzeichnis" ("Busoni Index"); sometimes the letters KiV for "Kindermann Verzeichnis" are used) followed by a numeric identifier, to identify his compositions and transcriptions. The identifier B (for "Bearbeitung", "arrangement") is used for Busoni's transcriptions and cadenzas. For example, BV B 1 refers to Busoni's cadenzas for Beethoven's Piano Concerto No. 4.