Standard ECMA-376 Office Open XML File Formats ECMA-376 This Standard defines Office Open XML's vocabularies and document representation and packaging. It also specifies requirements for consumers and producers of Office Open XML. Version 1st edition (December 2006) 2nd edition (December 2008) 3rd edition (June 2011) 4th edition (December 2012) 5th edition (Part 3, December 2015; and Parts 1 & 4, December 2016) Link https://www.ecma-international.org/publications/standards/Ecma-376.htm