<?xml version="1.0" encoding="UTF-8"?>

<!ELEMENT books (book+)>
<!ELEMENT book (genre, author+, title, placeofpub+, publisher, date, chapters+)>
<!ELEMENT genre EMPTY>
<!ATTLIST genre type CDATA #IMPLIED>
<!ELEMENT author (last,first)>
<!ELEMENT last (#PCDATA)>
<!ELEMENT first (#PCDATA)>
<!ELEMENT title (#PCDATA)>
<!ELEMENT placeofpub (city, state)><!-- I changed this to city and state child elements, so I changed (#PCDATA) to (city, state) and so on-->
<!ELEMENT city (#PCDATA)>
<!ELEMENT state (#PCDATA)>
<!ELEMENT publisher (#PCDATA)>
<!ELEMENT date EMPTY>
<!ATTLIST date when CDATA #REQUIRED>
<!ELEMENT chapters (chapter+)>
<!ELEMENT chapter (#PCDATA)>
<!ATTLIST chapter number CDATA #REQUIRED>