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
Term Catalogue omitting many; and refusing all under 1sh[illing] [in] Price; hath occasioned the Printing of this Catalogue: wherein those defects are rectified. Collected by, and printed for, the Booksellers of "London". A comparison of the numbers of titles listed in the late 17th and early 18th century term catalogues and numbers the English Short Title Catalogue provides justification for these complaints. The 161 catalogues printed between 1668 and 1711 show an increase in the number of titles. The average catalogue listed 109 books under 10 headings. Some catalogues had up to 13 headings; the minimum was six in the small catalogue