Paper 1 for PRES'99: Author(s): I.J. Halvorsen and S. Skogestad, Title: Use of Shortcut Methods to Analyse Optimal Operation of Petlyuk Distillation Columns ( Pres99-ShortCut..) Paper 2 for PRES'99: Author(s): I.J. Halvorsen, M. Serra, and S. Skogestad Title: Evaluation of Self-Optimizing Control Structures for an Integrated Petlyuk Distillation Column ( Pres99-SelfOpt...)