End MUL2.
Section INVARIANT6_ter.

(* Specifications: *)
Lemma ancestor_not_reflexive :
forall c : Config,
legal c -> forall s1 s2 : Site, ancestor c s1 s2 -> s1 <> s2.
Lemma ancestor_has_positive_st :
forall c : Config,
legal c -> forall s1 s2 : Site, ancestor c s1 s2 -> (st c s1 > 0)%Z.