Proofgold Proof

pf
Let x0 of type ι be given. Assume H0: ordinal x0. Apply minus_SNo_Lev with x0, λ x1 x2 . x2 = x0 leaving 2 subgoals. Apply ordinal_SNo with x0. The subproof is completed by applying H0. Apply ordinal_SNoLev with x0. The subproof is completed by applying H0. ■