@incollection{JEDP_1990____A18_0,
     author = {Laptev, Ari and Safarov, Yu},
     title = {Global solution of the wave equation},
     booktitle = {},
     series = {Journ\'ees \'equations aux d\'eriv\'ees partielles},
     eid = {18},
     pages = {1--9},
     publisher = {Ecole polytechnique},
     year = {1990},
     mrnumber = {91j:58161},
     zbl = {0719.58041},
     language = {en},
     url = {http://archive.numdam.org/item/JEDP_1990____A18_0/}
}