@incollection{AST_1973__2-3__143_0,
     author = {Duistermaat, J. J.},
     title = {On {Carleman} estimates for pseudo-differential operators},
     booktitle = {Colloque International C.N.R.S. sur les \'equations aux d\'eriv\'ees partielles lin\'eaires},
     series = {Ast\'erisque},
     pages = {143--151},
     publisher = {Soci\'et\'e math\'ematique de France},
     number = {2-3},
     year = {1973},
     mrnumber = {407423},
     zbl = {0274.35053},
     language = {en},
     url = {http://archive.numdam.org/item/AST_1973__2-3__143_0/}
}