<?xml  version="1.0"?>
<!-- validity constraint check for Production 56(Positive Test)-->
<!DOCTYPE test
 [
 <!ELEMENT test ANY>
 <!ELEMENT nametokens EMPTY>
 <!ATTLIST nametokens thistoken NMTOKENS #IMPLIED>
]>
<test>
<nametokens thistoken = "x:lang y:country"></nametokens>
In an attribute declaration, values of type NMTOKENS match the Nmtokens production
</test>