xml declaration in DTDs and encodings

[oliver sick <o.sick@gikom-cse.de>]

Hi,

Is it correct to start a DTD with the first line

  <?xml version="1.0" encoding="UTF-8" ?>
or even
  <?xml version="1.0" ?>

I'm a little bit confused. I've seen some DTDs with such a 
xml-declaration on the net and a lot more without. 
In my opinion it's not correct to use the xml-declaration, 
because a DTD is not xml. But I can't find such informations in 
the XML spec or in other ressources.  

On the other hand side if this declaration could not be used, 
how can I determine the character encoding of DTDs ?

tia
Oliver