End positive.
Section positive2.
Variable Site : Set.
Hypothesis eq_site_dec : eq_dec Site.
Variable LS1 : list Site.
Variable LS2 : list Site.
Variable Data : Set.
Let Table2 := Site -> Site -> Data.
Variable t : Table2.
Variable s0 s1 : Site.
Variable d0 : Data.
Variable f : Site -> Site -> Data -> Z.

Lemma sigma2_strictly_positive :
forall (x y : Site) (l1 l2 : list Site),
In x l1 ->
In y l2 ->
(forall x' y' : Site, (f x' y' (t x' y') >= 0)%Z) ->
(f x y (t x y) > 0)%Z -> (sigma2_table Site l1 l2 Data f t > 0)%Z.