Arendt, W., and R. Schätzle. “Semigroups Generated by Elliptic Operators in Non-Divergence Form on C-o(Ω)”. ANNALI SCUOLA NORMALE SUPERIORE - CLASSE DI SCIENZE, vol. 13, no. 2, June 2014, pp. 417-34, doi:10.2422/2036-2145.201111_010.