Section INVARIANT3.

Lemma sigma_rooted_fun1 :
forall (s s1 s2 : Site) (d : Message),
s2 <> owner ->
~ In s1 LS ->
~ In s2 LS ->
sigma_but Site owner eq_site_dec LS (fun s : Site => rooted_fun s s1 s2 d) =
0%Z.