The default encoding for XML is UTF-8. If your document doesn't use UTF-8, it needs to indicate the encoding it did use.

You appear to have the first of the following (or maybe no <?xml?> at all). You need to change it to the last.

<?xml version="1.0"?>                           UTF-8
<?xml version="1.0" encoding="UTF-8"?>          UTF-8
<?xml version="1.0" encoding="Windows-1252"?>   Windows-1252
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If you're not the one who is producing this bad XML, you can still easily fix it by applying a substitution before passing the XML to the XML parser.