The results in this paper, obtained with the co-authors, are an extended abstract of the presentation by Gen Nakamura at the IPMS2024 conference. The aim of this short paper is to provide some background for this study and show the essence of our new method to derive the relaxation tensor for the anisotropic extended Burgers models, which is one of a typical spring-dashpot model used to describe the rheological behavior of viscoelastic media. The major contribution of this method is that it works under quite general assumptions and gives the properties of the relaxation tensor. The usual method for deriving the relaxation tensor does not work in general for the extended Burgers model if its elasticity tensors of springs become anisotropic.