Columbia subject headings:
Differential equations, Nonlinear--Congresses.
Differential equations, Partial--Congresses.
Harvard subject headings:
Differential equations, Nonlinear--Congresses.
Differential equations, Nonlinear.
Differential equations, Partial--Congresses.
Differential equations, Partial.
Princeton subject headings:
Differential equations, Nonlinear.
Differential equations, Partial.