<!DOCTYPE test [
<!ELEMENT test (#PCDATA) >
<!ENTITY xx 'xyzzy' >
<!ENTITY yy 'xx;/bar' >
<!ENTITY zz '&xx;/bar' >
]>
<test tricky1="foo/#38;&yy;" tricky2="foo/&zz;" />

<!-- I think the result should be:
<test tricky1="foo/&xx;/bar" tricky2="foo/xyzzy/bar" />

because in the 'tricky1' case, only the substituted text for &yy; is 
reprocessed, not the entire attribute after subsitution of &yy;
?
-->