Columbia subject headings:
Boundary value problems.
Difference equations.
Differential equations, Partial.
Functional analysis.
Spectral theory (Mathematics)
Harvard subject headings:
Boundary value problems.
Difference equations.
Differential equations, Partial.
Functional analysis.
Spectral theory (Mathematics)
Princeton subject headings:
Boundary value problems.
Difference equations.
Differential equations, Partial.
Functional analysis.
Spectral theory (Mathematics)