(*#* **Examples of semi-groups: $\langle$#⟨#[Q],[[+]]$\rangle$#⟩# and $\langle$#⟨#[Q],[[*]]$\rangle$#⟩#
***$\langle$#⟨#[Q],[[+]]$\rangle$#⟩#
*)
(*#* **Examples of semi-groups: $\langle$#⟨#[Q],[[+]]$\rangle$#⟩# and $\langle$#⟨#[Q],[[*]]$\rangle$#⟩#
***$\langle$#⟨#[Q],[[+]]$\rangle$#⟩#
*)