@incollection{JEDP_1987____A1_0, author = {Lars H\"ormander}, title = {Remarks on the {Klein-Gordon} equation}, booktitle = {}, series = {Journ\'ees \'equations aux d\'eriv\'ees partielles}, eid = {1}, pages = {1--9}, publisher = {\'Ecole polytechnique}, year = {1987}, zbl = {0655.35057}, language = {en}, url = {https://proceedings.centre-mersenne.org/item/JEDP_1987____A1_0/} }