Skutella, Martin Algorithms and Complexity, MPI for Informatics, Max Planck Society;
Hall, A., Hippler, S., & Skutella, M. (2003). Multicommodity Flows Over Time: Efficient Algorithms and Complexity. In Automata, languages and programming: 30th International Colloquium, ICALP 2003 (pp. 397-409). Berlin, Germany: Springer.