Oxygen 18 implements 5.1

From the list of improvements in the newly released Oxygen 18:
The most commonly used documentation frameworks, DITA and DocBook have
been updated. oXygen now officially supports DITA 1.3 and the DITA Open
Toolkit recent version 2.2.3 is offered in addition to the stable 1.8.5
version. The DocBook stylesheets were updated to version 1.79.1 and
DocBook schemas to version 5.1.

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Bob Stayton Sagehill Enterprises