Space-time fractional Zener wave equation
  Space-time fractional Zener wave equation, describing viscoelastic materials obeying the time-fractional Zener model and the space-fractional strain measure, is derived and analyzed. This model includes waves with finite speed, as well as non-propagating disturbances. The existence and the uniqueness of the solution to the generalized Cauchy problem are proved. Special cases are investigated and numerical examples are presented. 
Teodor M. Atanackovic and Marko Janev and Ljubica Oparnica and Stevan   Pilipovic and Dusan Zorica
math-ph math.MP