Question:
Which employer did Laurent Schwartz work for in May, 1963?

Context:
 Laurent Schwartz works for École polytechnique from Jan, 1959 to Jan, 1980. 
 Laurent Schwartz works for Paris Diderot University from Jan, 1980 to Jan, 1983. 
 Laurent Schwartz works for Université de Nancy from Jan, 1945 to Jan, 1953. 
 Laurent Schwartz works for University of Paris from Jan, 1953 to Jan, 1959. 
 Laurent Schwartz works for Grenoble Alpes University from Jan, 1944 to Jan, 1945. 
 Laurent Schwartz works for National Center for Scientific Research from Jan, 1940 to Jan, 1942.

Answer:
École polytechnique