In the section "New Features and Enhancements" in "Elytron and the elytron Subsystem":

There are 2 links to 2 different books on how to configure Elytron subsystem. First one points to How to Configure Identity Management and the second to How to Configure Server Security.

The second link (the one pointing to How to Configure Server Security) points to section 2.1.2.1 "Create an Elytron Security Realm" instead of overall section 2.1.2 "Elytron Subsystem". This would also create better text in the release notes themselves:

see... Elytron Subsystem for more things you can do with Elytron.

instead of

see... Create an Elytron Security Realm for more things you can do with Elytron.

Same issue is with the third link inside the text, it should point to overall section "Elytron Subsystem" instead of "Create an Elytron Security Realm". So the text "You can find steps for enabling the Elytron configuration in the Create an Elytron Security Realm section." it should be "You can find steps for enabling the Elytron configuration in the Elytron Subsystem section."