Poem DTD:


<!ELEMENT POEM     (TITLE, AUTHOR, STANZA*)>
<!ELEMENT TITLE     (#PCDATA)>
<!ELEMENT AUTHOR    (FIRSTNAME, LASTNAME)>
<!ELEMENT FIRSTNAME    (#PCDATA)>
<!ELEMENT LASTNAME    (#PCDATA)>
<!ELEMENT STANZA     (LINE*)>
<!ELEMENT LINE     (#PCDATA)>
<!ATTLIST LINE N CDATA #REQUIRED>