Corollary 8.5. Assuming that:

• $F$ a formal group over $R$

• $n\in \mathbb{Z}$ such that $n\in R^{\times }$

• (i) $[n]:F\to F$ is an isomorphism of formal groups
• (ii) If $R$ is complete with respect to ideal $I$ then $F(I)\stackrel{\times n}{\to }F(I)$ is an isomorphism of groups. In particular, $F(I)$ has no $n$-torsion.