Columbia subject headings:
Differential equations, Partial.
Friedrichs, K. O. (Kurt Otto), 1901-1983.
Mathematics--Germany--Biography.
Spectral theory (Mathematics)
Harvard subject headings:
Differential equations, Partial.
Friedrichs, K. O. (Kurt Otto), 1901-1983
Mathematics--Germany--Biography.
Spectral theory (Mathematics)
Princeton subject headings: