External DTD errors

[cturcotte224]

I am working on an assignment for school and I am having trouble getting my code to work. The assignment in to write two different external DTDs for two different xml files. Then using a third xml file with an ixternal DTD, combine the other files into a single page, using ENTITY.
When I try too validate the combined file, pixal.xml, I get the error "Ln 19 Col 2 - The markup declarations contained or pointed to by the document type declaration must be well-formed."

When I try to validate the hwlist.xml file, I get the "Ln 50 Col 9 - An element with the identifier "PA80W" must appear in the document."

I have been over the code mulitple times and I can't find the error. I would really appreciate another pair of eyes to look over the code and point me in the right direction. Thank you for your time.

I have attached the three files that I appear to be having the issues with as .txt files. Pixal.txt is the xml file that joins the other two xml files together. hwlist.txt is on of the seperate xml files, and hw.txt is the DTD associated with hwlist.xml