@article{JEMS_2007_9_3_a5,
     author = {Barbara Brandolini and Cristina Trombetti},
     title = {Comparison results for {Hessian} equations via symmetrization},
     journal = {Journal of the European Mathematical Society},
     pages = {561--575},
     publisher = {mathdoc},
     volume = {9},
     number = {3},
     year = {2007},
     doi = {10.4171/jems/88},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/jems/88/}
}