Section INVARIANT3.

Lemma sigma_rooted_fun14 :
forall (s1 s2 : Site) (l : list Site),
s2 <> owner ->
s1 <> owner ->
only_once Site eq_site_dec s1 l ->
sigma_but Site owner eq_site_dec l (fun s : Site => rooted_fun s s1 s2 copy) =
1%Z.