“…Abstracting from the aforementioned electrical and power systems applications, several solutions to the sinusoidal estimation problem outlined above have been conceived in the system-theoretic and signal processing fields, and many results are given in terms of adaptive observers (see [11], [12], [13], [14], [15], [16], [17] among others), or nonlinear adaptive systems [18], [19], [20]. Notably, all of these methods formally guarantee the global stability of the estimator.…”