This version of Proof General has been tested with these Emacs versions
on Linux:

 Emacs 22.1.1		 -- recommended
 XEmacs 21.4.XX		 -- stable, but not recently tested
 XEmacs 21.5 (beta28)    -- tested, has patches for several XEmacs bugs

and prover versions:

 Coq 8.1
 Isabelle2005
 Isabelle2007

For more possibilities, please check and contribute here:
  
   http://proofgeneral.inf.ed.ac.uk/wiki/Main/PGEmacsVer37Final

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Backward compatibility makes the code into a bad mess.  Some compatibility
has been removed here, specifically affecting:

 Isabelle 2004

 Earlier buggy versions of Emacs 21  (21.4.1 should work)