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
Austrian Americans some 40,000 Austrians entered the United States. Since the 1960s, however, Austrian immigration has been negligible, mostly because Austria is now a developed nation, where poverty and political oppression are scarce. According to the 1990 U.S. census, 948,558 people claimed be of Austrian descent (only 0.4 percent of the total population). In the 19th century, a total of 4.2 million Austrians had immigrated to the United States. Austrian immigrants adapted quickly to American society because the Austrian Empire had also been a melting pot of many cultures and languages. On the other hand, despite the rejection that Austrians feel toward