theorem Th69:
  for R being NF-var terminating with_UN_property invariant stable
  ManySortedRelation of Free(S,X)
  for o,p for q being Element of Args(o, NFAlgebra R) st p = q
  holds R.the_result_sort_of o reduces o-term p, Den(o,NFAlgebra R).q
  proof
    let R be NF-var terminating with_UN_property invariant stable
    ManySortedRelation of Free(S,X);
    let o,p;
    let q be Element of Args(o, NFAlgebra R);
    assume p = q;
    then (canonical_homomorphism NFAlgebra R)#p = q by MSAFREE4:66;
    hence R.the_result_sort_of o reduces o-term p, Den(o,NFAlgebra R).q
    by Th98;
  end;
