@article{CRMATH_2007__344_9_559_0,
     author = {Cutr{\`\i}, Alessandra and Tchou, Nicoletta},
     title = {Fully nonlinear degenerate operators associated with the {Heisenberg} group: barrier functions and qualitative properties},
     journal = {Comptes Rendus. Math\'ematique},
     pages = {559--563},
     publisher = {Elsevier},
     volume = {344},
     number = {9},
     year = {2007},
     doi = {10.1016/j.crma.2007.03.003},
     language = {en},
     url = {http://www.numdam.org/articles/10.1016/j.crma.2007.03.003/}
}