(VAR x)
(RULES
  b -> a
  b -> c
  c -> c
  d -> c
  d -> e
  f(x,a) -> A
  f(x,e) -> A
  f(x,A) -> A  
  f(c,x) -> A
)
(COMMENT
[111] p. 30 (GUN & ~UN & ~GUNC)
)