What in the world seem to have problem with entity piece?
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE stylesheet[<!ENTITY UPPERCASE "ABCDEFGHIJKLMNOPQRSTUVWXYZ">
<!ENTITY LOWERCASE "abcdefghijklmnopqrstuvwxyz">
<!ENTITY UPPERCASE_TO_LOWERCASE "'&UPPERCASE;' , '&LOWERCASE;'">
<!ENTITY LOWERCASE_TO_UPPERCASE "'&LOWERCASE;' , '&UPPERCASE;'">]>
<xsl:stylesheet>
<!-- LINES OF CODE -->
</xsl:stylesheet>