Columbia subject headings:
Differential equations, Partial--Congresses.
Eigenvalues--Congresses.
Maximum principles (Mathematics)--Congresses.
Harvard subject headings:
Differential equations, Partial--Congresses.
Eigenvalues--Congresses.
Maximum principles (Mathematics)--Congresses.
Princeton subject headings:
Differential equations, Partial--Congresses.
Eigenvalues--Congresses.
Maximum principles (Mathematics)--Congresses.