When parsing formula ='C:\[ex45672.xls]d f'!$B$13, FormulaParser does not recognize is as a reference to an external workbook. Instead, it creates an org.apache.poi.ss.formula.ptg.Ref3DPxg [sheet=[1]d f ! $B$13] token where externalWorkbookNumber = -1 and firstSheetName = "[1]d f"