Differences and similarities with well-known models are discussed. At first is one illustration to explain CT principle by Maxwell model and scale arrangement[aut]Pääkkönen, E.J.” . Viscoelastic constitutive equations from control theory is derived purely from the standpoint of polymer structure, even though the model was originally developed for detecting the MWD. Microlevel structures and long-chain branches from viscoelastic measurements are discussed earlies.