The stylesheet uses node-set function, and Muenchian
  Grouping (over a RTF) .. 

It _needs_ to use a node-set function, but as posted you did not use it
(you need common:node-set($rtf))

  The stylesheet is tested with Saxon 8.4.

It's best not to test xslt 1 stylesheets with an xslt2 processor.
As (as in this case) many things that generate an error in xslt1 will
not be reported.

David



________________________________________________________________________
This e-mail has been scanned for all viruses by Star. The
service is powered by MessageLabs. For more information on a proactive
anti-virus service working around the clock, around the globe, visit:
http://www.star.net.uk
________________________________________________________________________