<!-- simple dtd for business letter. refer to it as buslet.dtd -->
<!ELEMENT letter O O (date, address, salutation, body, close, signature)>
<!ELEMENT date O O (#PCDATA)>
<!ELEMENT address O O (line)+>
<!ELEMENT salutation O O (line)>
<!ELEMENT body O O (P)+>
<!ELEMENT close O O (line)>
<!ELEMENT signature O O (line)+>
<!ELEMENT (line | P ) O O(#PCDATA |I)*>
<!ELEMENT I O O (#PCDATA)