text: public ExternalSheet getExternalSheet(int externSheetIndex) {ExternalSheet sheet = _iBook.getExternalSheet(externSheetIndex);if (sheet == null) {int localSheetIndex = convertFromExternSheetIndex(externSheetIndex);if (localSheetIndex == -1) {return null;}if (localSheetIndex == -2) {return null;}String sheetName = getSheetName(localSheetIndex);int lastLocalSheetIndex = _iBook.getLastSheetIndexFromExternSheetIndex(externSheetIndex);if (lastLocalSheetIndex == localSheetIndex) {sheet = new ExternalSheet(null, sheetName);} else {String lastSheetName = getSheetName(lastLocalSheetIndex);sheet = new ExternalSheetRange(null, sheetName, lastSheetName);}}return sheet;}