OpenDocument - Wikipedia
https://en.wikipedia.org/wiki/OpenDocument
The Open Document Format for Office Applications (ODF), also known as OpenDocument, is a ZIP-compressed XML-based file format for spreadsheets, charts...
ODF File Extension - What is an .odf file and how do I open it?
https://fileinfo.com/extension/odf
An ODF file is a document created by Apache OpenOffice Math, a program used for creating math formulas. It contains one or more mathematical equations and may also contain macros.
About ODF
http://www.opendocumentformat.org/aboutODF/
About OpenDocument Format. Open Document Format (ODF) ODF is not software, but a universal method of storing and processing information that transcends specific applications and providers.
Using Open Document Formats (ODF) in your organisation - GOV.UK
https://www.gov.uk/guidance/using-open-document-formats-odf-in-your-organisation
This guidance is an introduction to the Open Document Format (ODF) standard and how you can select ODF-compliant solutions. Selecting your ODF-compliant solution. ODF compatible software.
OASIS Open Document Format for Office Applications...
https://www.oasis-open.org/committees/tc_home.php?wg_abbrev=office
The OpenDocument Format (ODF) is an open XML-based document file format for office applications to be used for documents containing text, spreadsheets, charts, and graphical elements.