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• http://www.cambridgesoft.com/support/DesktopSupport/KnowledgeBase/SystemRequirements/

• http://disq.us/p/z7dtk1

End of mainstream support (no more security patching) for Microsoft Office 2011 on October 2017

• https://support.microsoft.com/en-us/lifecycle/search/?p1=15627 

Also, support may end simply by virtue of new Mac OS's. For example, macOS 10.13 "High Sierra" has a new file system (APFS). Although APFS nominally may run any software newer than ~2009, might not for some specifically such as MS Office 2011. Example:

• https://www.neowin.net/news/microsoft-says-office-for-mac-2011-will-not-be-supported-on-macos-1013-high-sierra?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+neowin-main+%28Neowin+News%29

Microsoft changed how pasting works in Office 2016 for the Mac

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