“…In fact, the Holt potentials have been studied by many authors making use of different approaches (Painlevé analysis [4], the direct method [6], Lax equations [8], relation with the Drach potentials [10,30], Lie symmetries [7], scaling symmetries [16]), but in spite of this, we see that they are endowed with certain properties that still remain to be studied. Now, concerning the relation of the superintegrable potential U with the Holt potentials we consider that there are two interesting points to be studied: (i) the existence of higher-dimensional versions of the Holt potentials [26] as a method for obtaining potentials similar to U but with three or more degrees of freedom, and (ii) the duality and coupling-constant metamorphosis between integrable Hamiltonian systems [27,28], and, more specifically, the relation of the Holt potential with the Hénon-Heiles-type Hamiltonians [29] can also lead to the construction of other superintegrable systems.…”