 X:Top. 
reduce(
X:Top. 
reduce( t,vs. term_free_vars(t) @ vs;nil;v) = nil
t,vs. term_free_vars(t) @ vs;nil;v) = nil 
 (list_accum(x,t.x([[t]] 1of(e) s s' a1 tr);X;v) ~ list_accum(x,t.x([[t]] 1of(e) s s' a2 tr);X;v))
 
(list_accum(x,t.x([[t]] 1of(e) s s' a1 tr);X;v) ~ list_accum(x,t.x([[t]] 1of(e) s s' a2 tr);X;v)) 
  X:Top. 
(term_free_vars(u) @ reduce(
X:Top. 
(term_free_vars(u) @ reduce( t,vs. term_free_vars(t) @ vs;nil;v)) = nil
t,vs. term_free_vars(t) @ vs;nil;v)) = nil 
 ...
 
...| 1 | 11. X: Top 12. (term_free_vars(u) @ reduce(  t,vs. term_free_vars(t) @ vs;nil;v)) = nil  list_accum(x,t.x
 ([[t]] 1of(e) s s' a1 tr);X
 ([[u]] 1of(e) s s' a1 tr);v) ~ list_accum(x,t.x
 (...);...;v) | 
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