text: public override String ToFormulaString(){StringBuilder sb = new StringBuilder();if (externalWorkbookNumber >= 0){sb.Append('[');sb.Append(externalWorkbookNumber);sb.Append(']');}if (sheetName != null){sb.Append(sheetName);}sb.Append('!');sb.Append(ErrorConstants.GetText(ErrorConstants.ERROR_REF));return sb.ToString();}