public Area3DPxg(int externalWorkbookNumber, SheetIdentifier sheetName, AreaReference arearef) {super(arearef);this.externalWorkbookNumber = externalWorkbookNumber;this.firstSheetName = sheetName.getSheetIdentifier().getName();if (sheetName instanceof SheetRangeIdentifier) {this.lastSheetName = ((SheetRangeIdentifier)sheetName).getLastSheetIdentifier().getName();} else {this.lastSheetName = null;}}