I'm afraid XSLT has very limited support for unparsed entities. In XSLT 1.0 this is limited to the unparsed-entity-uri() function, which allows you to determine the system ID of an entity if you know its name. In XSLT 2.9 this is supplemented by unparsed-entity-public-id(), which allows you to discover the public ID as well. But there is no way of discovering the names of the entities that have been declared. (As the shopkeepers always say, there's no demand for it luv, no-one buys unparsed entities these days...)
Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference