## Summary

Formalization of a part of [11]. Unfortunately, not all is possible to be formalized. Namely, in the paper there is a mistake in the proof of Lemma 3. It states that there exists *x* ∈ *M*_{1} such that *M*_{1}(*x*) > *N*_{1}(*x*) and (∀*y* ∈ *N*_{1})*x* ⊀ *y*. It should be *M*_{1}(*x*) ⩾ *N*_{1}(*x*). Nevertheless we do not know whether *x* ∈ *N*_{1} or not and cannot prove the contradiction. In the article we referred to [8], [9] and [10].

## Comments (0)