Modular DocBook

Hello,

I have created two sections that I would like to integrate into a
chapter. I have based my own files on Bob Stayton's Ch. 23 Modular
DocBook Files. After transformation from xml to html, I cannot navigate
to the two sections. There is likely some elementary error that I'm not
seeing, but I'm new to DocBook.

Using the xsltproc transform for HTML and the chunk.xls style sheet,
I'm 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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Thanks in advance for reviewing my code.

Betty