Let x0 of type ι be given.
Apply SNoLev_prop with
x0,
x0 = PSNo (SNoLev x0) (λ x1 . x1 ∈ x0) leaving 2 subgoals.
The subproof is completed by applying H0.
Apply SNo_PSNo_eta_ with
SNoLev x0,
x0 leaving 2 subgoals.
The subproof is completed by applying H1.
The subproof is completed by applying H2.