External DTDs

Usually a DTD is external to the document:

<!DOCTYPE anthology SYSTEM "antology.dtd">

<!DOCTYPE anthology SYSTEM "antology.dtd" []>

<!DOCTYPE cesCorpus PUBLIC "-//CES//DTD cesDoc//EN">

<!DOCTYPE cesCorpus PUBLIC "-//CES//DTD cesDoc//EN"
[
  <!ENTITY mte1984-en PUBLIC 
           "-//MTE//TEXT CES1 1984//EN">
...
  <!ENTITY mte1984-ro PUBLIC 
           "-//MTE//TEXT CES1 1984//RO">
  <!ENTITY mte1984-sl PUBLIC 
           "-//MTE//TEXT CES1 1984//SL">
]>
<cesCorpus id="o" version="0.1">
  <cesHeader> ... </cesHeader>
  &mte1984-en;
...
  &mte1984-ro;
  &mte1984-sl;
</cesCorpus>