DocBook MathML Module comment/question

Shouldn't there be this declaration in "dbmatml.dtd" to handle inline
equations? :
<!ENTITY % inlineequation.content "(alt?,
    (graphic+|inlinemediaobject+|mml:math))">

The description says, that dbmathml.dtd should handle mathml inside
<inlineequation>, but it doesn't.

The document www.oasis-open.org/docbook/xml/mathml/1.0/testmath.xml
is valid, but if I insert <inlineequation> with mathml, it is no more
(I use XMLSpy, it says - Unexpected child element 'mml:math')

There is an example of including mathml in docbook by including mathml
dtd directly in document:
http://www.sagehill.net/docbookxsl/MathML.html

and there is this line, which (I think) is missing in dbmathml.dtd :

<!ENTITY % inlineequation.content "(alt?,
    (grahic+|inlinemediaobject+|mml:math))">

thanks