@article{RSMUP_1989__81__85_0,
     author = {Del Santo, Daniele},
     title = {Uniqueness of the {Cauchy} problem for a second order operator},
     journal = {Rendiconti del Seminario Matematico della Universit\`a di Padova},
     pages = {85--93},
     publisher = {Seminario Matematico of the University of Padua},
     volume = {81},
     year = {1989},
     mrnumber = {1020188},
     zbl = {0699.35039},
     language = {en},
     url = {http://archive.numdam.org/item/RSMUP_1989__81__85_0/}
}