@article{RLIN_1993_9_4_3_a5,
     author = {Citti, Giovanna},
     title = {A comparison theorem for the {Levi} equation},
     journal = {Atti della Accademia nazionale dei Lincei. Rendiconti Lincei. Matematica e applicazioni},
     pages = {207--212},
     publisher = {mathdoc},
     volume = {Ser. 9, 4},
     number = {3},
     year = {1993},
     zbl = {0822.35009},
     mrnumber = {262881},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/RLIN_1993_9_4_3_a5/}
}