On the existence, uniqueness and regularity of solutions of a   viscoelastic Stokes problem modelling salt rocks
  A Stokes-type problem for a viscoelastic model of salt rocks is considered, and existence, uniqueness and regularity are investigated in the scale of $L^2$-based Sobolev spaces. The system is transformed into a generalized Stokes problem, and the proper conditions on the parameters of the model that guarantee that the system is uniformly elliptic are given. Under those conditions, existence, uniqueness and low-order regularity are obtained under classical regularity conditions on the data, while higher-order regularity is proved under less stringent conditions than classical ones. Explicit estimates for the solution in terms of the data are given accordingly. 
R. A. Cipolatti, I.-S. Liu, L. A. Palermo, M. A. Rincon, R. M. S. Rosa
math.AP