1. L. D. Hankins, ?Dynamic stress in a thick-walled spherical shell of Voight material,? AIAA J.,71, No. 11, 2038?2039 (1966).
2. K. C. Valanis and S. T. Sun, ?Axisymmetric wave propagation in a solid viscoelastic sphere,? Int. J. Eng. Sci.,5, No. 12, 939?956 (1967).
3. S. Stoeren, ?Analysis of spherically and cylindrically divergent stress pulses in linear viscoelastic solids,? Achta Polytechn. Scand. (Physics including Nucleonics),55, 36 (1968).
4. V. G. Karnaukhov, V. I. Kozlov, and N. K. Kucher, ?Dynamic behavior of reinforces elastic and viscoelastic spheres,? Mekh.Polim., No. 5, 875?881 (1976).
5. S. W. Bhattacharya and S. W. Chatterjee, ?On the propagation of spherical waves in viscoelastic medium,? Indian J. Meteorol. Geophys.,21, No. 4, 553?566 (1970).