<!DOCTYPE RECURSIVE
[
<!ELEMENT RECURSIVE     - - (A | B | C)*>
<!ELEMENT A             - o (#PCDATA)>
<!ELEMENT B             - o (#PCDATA)>
<!ELEMENT C             - o (#PCDATA)>
]>

<RECURSIVE>
<A>one
<B>two
<A>three
<C>four
</RECURSIVE>

