@article{SEDP_1981-1982____A21_0,
     author = {Fefferman, C. and Phong, D. H.},
     title = {Lower bounds for pseudo-differential operators},
     journal = {S\'eminaire \'Equations aux d\'eriv\'ees partielles (Polytechnique) dit aussi "S\'eminaire Goulaouic-Schwartz"},
     note = {talk:22},
     pages = {1--6},
     publisher = {Ecole Polytechnique, Centre de Math\'ematiques},
     year = {1981-1982},
     language = {en},
     url = {http://www.numdam.org/item/SEDP_1981-1982____A21_0/}
}