EN
For every closed subset C in the dual space $Ĥ_n$ of the Heisenberg group $H_n$ we describe via the Fourier transform the elements of the hull-minimal ideal j(C) of the Schwartz algebra $S(H_n)$ and we show that in general for two closed subsets $C_1, C_2$ of $Ĥ_n$ the product of $j(C_1)$ and $j(C_2)$ is different from $j(C_1∩C_2)$.