Columbia subject headings:
Bifurcation theory.
Functional equations.
Maxima and minima.
Singularities (Mathematics)
Symmetry groups.
Harvard subject headings:
Bifurcation theory.
Functional equations.
Maxima and minima.
Singularities (Mathematics)
Symmetry groups.
Princeton subject headings:
Bifurcation theory.
Broken symmetry (Physics)