The stay of Prof. Dr. Volodymyr Derkach at the TU Ilmenau was very fruitful. I’m very satisfied about the results we achieved. In addition, the cooperation gave raise to numerous new questions and open problems. I am sure that this successful cooperation will continue. Prof. Dr. Volodymyr Derkach gave several courses at the TU Ilmenau (approx. 4 SWS per semester). Towards the end his German language skills were sufficient to teach his classes in German. He prepared his courses very carefully and he received a very positive feedback from his students. The stay by Prof. Dr. Volodymyr Derkach has led to numerous publications. The collaboration with various members of the institute at the TU Ilmenau was particularly gratifying. He used to have intense discussions with Priv.-Doz. Dr. Henrik Winkler, Dr. Friedrich Philipp, as well as with the doctoral student M.Sc. Hannes Gernandt, M.Sc. Florian Leben, M.Sc. Philipp Schmitz and M.Sc. Dmytro Strelnikov. Through many conversations and discussions with students and our PhD students, Prof. Dr. Volodymyr Derkach paved the way to new promising projects. He contributed to a very constructive and inspiring work atmosphere at our institute.