@article{SEDP_1980-1981____A25_0,
     author = {Fefferman, C. and Phong, D. H.},
     title = {Pseudo-differential operators with positive symbols},
     journal = {S\'eminaire \'Equations aux d\'eriv\'ees partielles (Polytechnique) dit aussi "S\'eminaire Goulaouic-Schwartz"},
     note = {talk:23},
     pages = {1--9},
     publisher = {Ecole Polytechnique, Centre de Math\'ematiques},
     year = {1980-1981},
     zbl = {0483.35085},
     language = {en},
     url = {http://archive.numdam.org/item/SEDP_1980-1981____A25_0/}
}