The Pioneers of the Mittag-Leffler Functions in Dielectrical and Mechanical Relaxation Processes

We start with a short survey of the basic properties of the Mittag-Leffler functions. Then we focus on the key role of these functions to explain the after-effects and relaxation phenomena occurring in dielectrics and in viscoelastic bodies. For this purpose we recall the main aspects that were formerly discussed by two pioneers in the years 1930’s-1940’s whom we have identified with Harold T. Davis and Bernhard Gross.