Opus number developed other catalogue-number systems; among them the "Bach-Werke-Verzeichnis" (BWV-number), and the "Köchel-Verzeichnis" (K- and KV -numbers) with which are organised the works of Johann Sebastian Bach and Wolfgang Amadeus Mozart, respectively. In the classical period, the Latin word "opus" ("work", "labour") was used to identify, list, and catalogue a work of art. By the 15th and 16th centuries, the word "opus" was used by Italian composers to denote a specific musical composition, and by German composers for collections of music. In compositional practise, numbering musical works in chronological order dates from 17th century Italy, especially Venice. In common usage, the
Star catalogue reworking of this catalogue in 1846 added reference numbers to the stars that are used to refer to some of these stars to this day. The decent accuracy of this catalogue kept it in common use as a reference by observatories around the world throughout the 19th century. The "Bonner Durchmusterung" ("German": Bonn sampling) and follow-ups were the most complete of the pre-photographic star catalogues. The "Bonner Durchmusterung" itself was published by Friedrich Wilhelm Argelander, Adalbert Krüger, and Eduard Schönfeld between 1852 and 1859. It covered 320,000 stars in epoch 1855.0. As it covered only the northern sky and some