“…for each k ∈ N, and that the functional Φ + λΨ has no global minimum, it is necessary to use some sequences of functions defined ad hoc. Generally, in these functions the norm of the variable is raised to a suitable power which depends on the nature of the problem and that gives them the requested regularity properties: in some applications the norm is used without power (see, for instance, [3,7,14,15,23,27,39]), in some others it is raised to the second ( [9,10,29,33,35,36])…”