This chapter collects several unrelated results and remarks concerning various topics discussed throughout the monograph. These include: a self-contained proof of Desch’s perturbation theorem; a suitable bounded variation (BV) condition underlying Miyadera perturbations; a spectral gap property for general weighted Laplacians on non-compact Riemannian manifolds; a predual approach to \(L^{p}\ \) spectral properties of neutron transport; and a short discussion of symmetrizable operators arising in Transport Theory.