Journal Article 2 Well-posedness Convergence analysis 1 Fractional Jacobi functions (FJFs) 1 Implicit material response 1 Linear-fractional singularity 1 Mixed variational formulation 1 mehr ... Non-linear systems of multi-order fractional differential equations (SMFDEs) 1 Nonlinear elasticity 1 Porous metals 1 Quasi-linear elliptic problem 1 Regularization 1 Spectral Galerkin method 1 Thresholding 1 Volumetric-deviatoric decomposition 1 weniger ...