Let x0 of type ι be given.
Let x1 of type ι be given.
Assume H3:
∀ x2 . x2 ∈ x0 ⟶ SNo x2.
Assume H4:
∀ x2 . x2 ∈ x1 ⟶ SNo x2.
Apply H7 with
minus_SNo (minus_SNo (SNoCut x0 x1)) = SNoCut x0 x1.
Apply minus_SNo_invol with
SNoCut x0 x1.
Apply SNoCutP_SNo_SNoCut with
x0,
x1.
The subproof is completed by applying H0.