assembly reference not found /mobile support ????

[lksstr]

Hi i am using Excel4Unity in my unity android project where i am exporting gradle of unity project and i am getting error of missing assembly reference

Assets\Excel4Unity\Excel.cs(4,7): error CS0246: The type or namespace name 'OfficeOpenXml' could not be found (are you missing a using directive or an assembly reference?)

Assets\Excel4Unity\ExcelHelper.cs(3,7): error CS0246: The type or namespace name 'OfficeOpenXml' could not be found (are you missing a using directive or an assembly reference?)

Assets\Excel4Unity\Excel.cs(16,18): error CS0246: The type or namespace name 'ExcelWorkbook' could not be found (are you missing a using directive or an assembly reference?)

please help me out