“…In spite of these difficulties, further efforts are currently being carried out to find alternative formulations to ÀQM, and we quote [6,7] by way of example. However, the most consistent impulse to ÀQM in recent times is the development of the real Hilbert space approach [8,9], where the Ehrenfest theorem has been proven, and a diversified collection of results has been obtained [10,11,12,13,14,15,16]. These outcomes within the non-relativistic theory suggested the hypothesis of a relativistic ÀQM, whose first achievement was established by the solution of the quaternionic Klein-Gordon equation (ÀKGE) [17].…”