Columbia subject headings:
Differential equations, Hyperbolic--Congresses.
Pseudodifferential operators--Congresses.
Harvard subject headings:
Differential equations, Hyperbolic--Congresses.
Differential equations, Partial--Congresses.
Pseudodifferential operators--Congresses.
Princeton subject headings:
Differential equations, Hyperbolic--Congresses.
Differential equations, Partial--Congresses.