“…Wayland (9) and Harris (13), among others, stated reservations concerning the applicability of the Maxwell relations to unsteady flow. Recent investigations, which include independent determination of primary normal stress, by Janeschitz-Kriegl and coworkers (14,15) on polymer melts support the validity of the linear law for these melts in transient experiments involving suddenly-imposed constant shear or sudden cessation of steady shear flow.…”