+<!ELEMENT illustrations ( illustration | illgroup )*>
+<!ATTLIST illustrations
+ %core.attributes;
+>
+<!--
+
+The "illustrations" element represents a collection of illustrations.
+The illustrations, or illustration groups, should be listed in the
+order they appear in the book.
+
+Example:
+
+ <illustrations>
+ <illustration . . . />
+ <illgroup . . .>. . .</illgroup>
+ . . .
+ </illustrations>
+
+-->
+
+<!ELEMENT illgroup ( illustration )*>
+<!ATTLIST illgroup
+ %core.attributes;
+ %link.attributes;
+>
+
+<!--
+
+The "illgroup" element represents a group of illustrations contained
+within one section. It is used when individual links to the each
+illustration from the illustrations index are not wanted.
+
+Example:
+
+ <illgroup idref=". . .">
+ <illustration . . . />
+ <illustration . . . />
+ . . .
+ </illgroup>
+
+ <illgroup idref=". . ." class="hidden">
+ <illustration . . . />
+ <illustration . . . />
+ . . .
+ </illgroup>
+
+-->
+