@article{RSMUP_1991__86__111_0,
     author = {Colombini, Ferruccio and Del Santo, Daniele},
     title = {Some uniqueness results for degenerate elliptic operators in two variables},
     journal = {Rendiconti del Seminario Matematico della Universit\`a di Padova},
     pages = {111--129},
     publisher = {Seminario Matematico of the University of Padua},
     volume = {86},
     year = {1991},
     mrnumber = {1154102},
     zbl = {0766.35005},
     language = {en},
     url = {http://www.numdam.org/item/RSMUP_1991__86__111_0/}
}