This chapter is concerned with the study of problems of the form (∂t,νMn(∂t,ν)+A)Un=F (∂ t,ν Mn(∂ t,ν )+A)Un=F for a suitable sequence of material laws (Mn)n when A ≠ 0. The aim of this chapter will be to provide the conditions required for convergence of the material law sequence to imply the existence of a limit material law M such that the limit U =limn→∞Un exists and satisfies (∂t,νM(∂t,ν)+A)U=F. (∂ t,ν M(∂ t,ν )+A)U=F.
