Modular DocBook still not working

Thanks to Remko, Camille, and Thomas for your suggestions. I have since
modified SectionA and SectionB accordinly; Chapter is still the same as
before.
 
I am still getting the following errors:

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Element include in namespace 'http://www.w3.org/2001/XInclude'
encountered in chapter, but no template matches.

Element include in namespace 'http://www.w3.org/2001/XInclude'
encountered in chapter, but no template matches.

Writing index.html for chapter

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What else am I still missing? Suggestions are welcome.

Betty