Let x0 of type ι be given.
Apply SNoLev_ordinal with
x0.
The subproof is completed by applying H0.
Apply ordinal_ordsucc with
SNoLev x0.
The subproof is completed by applying L1.
Apply SNoS_SNoLev with
x0.
The subproof is completed by applying H0.
Apply minus_SNo_Lev_lem1 with
ordsucc (SNoLev x0),
x0 leaving 2 subgoals.
The subproof is completed by applying L2.
The subproof is completed by applying L3.