The XML file with a internal DTD subset and a call for an external dtd subset name.dtd:
<?xml version="1.0" encoding="ISO-8859-15"?>
<!DOCTYPE person SYSTEM "name.dtd" [
><!ELEMENT person (name, profession*)>
<!ELEMENT profession (#PCDATA)>
]>
<person>
<name>
<first_name>
Alan</first_name>
<last_name>Turing</last_name>
</name>
<profession> matematician</profession>
<profession>cryptographer</profession>
<profession>computer scientist</profession>
</person>
---- the external dtd subset: name.dtd:
<?xml version="1.0" encoding="ISO-8859-15"?>
<!ELEMENT name (first_name, last_name)>
<!ELEMENT first_name (#PCDATA)>
<!ELEMENT last_name (#PCDATA)>