<!ELEMENT html (head, body)>
<!ELEMENT head (title)>
<!ELEMENT title (#PCDATA)>
<!ELEMENT body (h1|h2|h3|p|address)*>
<!ELEMENT h1 (a, #PCDATA)*>
<!ELEMENT h2 (a, #PCDATA)*>
<!ELEMENT h3 (a, #PCDATA)*>
<!ELEMENT p (a, #PCDATA)*>
<!ELEMENT address (a|img|#PCDATA)*>
<!ELEMENT a #PCDATA>
<!ATTLIST a
  href CDATA #IMPLIED
  name NMTOKENS #IMPLIED>
<!ELEMENT img EMPTY>
<!ATTLIST img
  src CDATA #REQUIRED>