Recent developments in research have added much to our understanding of Mendelssohn. Of crucial importance to scholars has been the re-emergence in Krakow of the large number of Mendelssohn manuscripts with had been thought lost after the removal from Berlin during World War II. Virtually all Mendelssohn's manuscripts are once again available for study, following the discovery of material previously thought lost during World War II. Peter Ward Jones took account of this in amending the text and appendices for this (1990) edition.