Automorphisms of Sylow $p$-subgroups of Chevalley groups over $p$-primary residue rings of integers

In this paper, we prove that any automorphism of a Sylow $p$-subgroup of the Chevalley group over the ring $\mathbb Z_{p^m}$ (where $p$ is prime and $m\geq 1$) is a product of graph, inner, diagonal, and hypercentral automorphisms.