is a format developed by Sony for its proprietary Sony Reader devices. Files in this format may contain text and images. The format is XML-based.
XLSX is a file format created with Microsoft Excel, version from 2007 and younger. This file is a spreadsheet. All data distributed document and stored in the cells. Each cell has a unique address, which is denoted by the letters and Arabic numerals. XLSX file format is based on the Open XML. To reduce the size of the file is compressed ZIP.