Let G be a locally compact
abelian group with dual group Γ, and let A denote a closed subalgebra of
A(Γ), the algebra of all Fourier transforms of functions in L1(G), which
separates the points of Γ, and whose members do not all vanish at any one
point on Γ. Then ReA ⋅ReA ⊂ReA implies A = A(Γ) if Γ is totally
disconnected.