R.  Kakar, K.  Kaur, K.C.  Gupta, 
    Study of Viscoelastic Model for Longitudinal Wave Propagation in a Non-Homogeneous Viscoelastic Filament,
    Journal of Modern Mathematics and Statistics,
    Volume 7,Issue 3,
    2013,
    Pages 26-31,
    ISSN 1994-5388,
    jmmstat.2013.26.31,
    (https://makhillpublications.co/view-article.php?doi=jmmstat.2013.26.31)
    Abstract: This study is concerned to check the validity of a five parameter 
  viscoelastic model for longitudinal wave propagating in the non-homogeneous 
  viscoelastic rods. In this study, it is assumed that density (ρ), rigidity 
  (G) and viscosity (η) of the specimen, i.e., rod are space dependent and 
  obey the laws <img src="http://docsdrive.com/images/medwelljournals/jmmstat/2013/img1-2k13-26-31.gif" width="54" height="14" align="absmiddle"> 
  <img src="http://docsdrive.com/images/medwelljournals/jmmstat/2013/img2-2k13-26-31.gif" width="133" height="16" align="absmiddle"> 
  . The method of non-linear partial differential equation (Eikonal equation) 
  has been used for finding the dispersion equation of longitudinal waves.
    Keywords: Longitudinal waves;variable density;viscoelastic media;Friedlander series;India