  Let $\Omega$ be an operator semigroup with generator $A$ in a sequentially
complete locally convex topological vector space $E$. For a semigroup with
generator $A+D$, where $D$ is a bounded linear operator on $E$, two integral
equations are derived. A theorem on continuous dependence of a semigroup on its
generator is proved. An application to random walk on $\mathbb{Z}$ is given.
