In their 1959 seminal paper Aharonov and Bohm showed, as Ehrenberg and Si-day earlier [1], that in quantum mechanics potentials have a significance that goes beyond that of a mere convenient mathematical tool, as is the case in classical mechanics. This essentially arises from the fact that in quantum mechanics the potentials themselves enter the Schrödinger equation, while in classical mechanics they affect the motion of particles only through their derivatives. To illustrate their conclusions Aharonov and Bohm (AB) proposed two effects in electron interference experiments: the electric or scalar AB effect, resulting from a non-zero electrostatic potential, and the magnetic or vector AB effect, resulting from a non-zero magnetic vector potential.