@article{CRMATH_2006__342_12_909_0,
     author = {Ralph Chill and Eva Fa\v{s}angov\'a and Giorgio Metafune and Diego Pallara},
     title = {The sector of analyticity of nonsymmetric submarkovian semigroups generated by elliptic operators},
     journal = {Comptes Rendus. Math\'ematique},
     pages = {909--914},
     publisher = {Elsevier},
     volume = {342},
     number = {12},
     year = {2006},
     doi = {10.1016/j.crma.2006.04.003},
     language = {en},
}