This application is a License Key of the "Workbook Maker".
You have to install "Workbook Maker" on your device.
Since this application is a plug-in format, it cannot be opened by the application alone.
"Workbook Maker" is an application which can create Self-Study Workbooks in your smartphone.
You can create Self-Study Workbooks from your notes, screenshots, books, or PDFs, etc., then you can memorize them very efficiently.