Köchel catalogue Anh. A have been identified since 1965 as by Leopold Mozart. Many works in Anh. C have since been more reliably assigned to other composers, or to Mozart himself. To maintain as much of the original K-numbering of the list as possible, while re-ordering in the revised, chronological sequence, letters were added to the new numbers. The following list shows Köchel's original designation (K) and the sixth edition (K). Other addenda and supplements to the catalogue are marked "." (This has been abbreviated to 'Anh.' in the list below.) Works listed as composed for piano were most likely performed on
19th century in science later in the 19th century by the German mathematician Bernhard Riemann; here no parallel can be found and the angles in a triangle add up to more than 180°. Riemann also developed Riemannian geometry, which unifies and vastly generalizes the three types of geometry. The 19th century saw the beginning of a great deal of abstract algebra. Hermann Grassmann in Germany gave a first version of vector spaces, William Rowan Hamilton in Ireland developed noncommutative algebra. The British mathematician George Boole devised an algebra that soon evolved into what is now called Boolean algebra, in which the only numbers were