The 1909 "The Count of Luxemburg" was by a composer whose best known and most successful operetta was what?
Franz Lehár: Franz Lehár (Hungarian: "Lehár Ferenc" ; 30 April 1870 – 24 October 1948) was an Austro-Hungarian composer. Franz Lehár:  He is mainly known for his operettas, of which the most successful and best known is "The Merry Widow" ("Die lustige Witwe").
i don't know