Approximation Hardness of Deadline-TSP Reoptimization, Hans-Joachim Böckenhauer, Joachim Kneis, Joachim Kupke, Theory of Computing Systems, vol. 410 (2009), pp. 2241-2249.
Binary operations on automatic functions, Juhani Karhumäki, Jarkko Kari, Joachim Kupke, RAIRO-Theor. Inf. Appl., vol. 42 (2008), pp. 217-236.
On the Approximability of TSP on Local Modifications of Optimally Solved Instances, Hans-Joachim Böckenhauer, Luca Forlizzi, Juraj Hromkovič, Joachim Kneis, Joachim Kupke, Guido Proietti, Peter Widmayer, Algorithmic Operations Research, vol. 2/2 (2007), pp. 83-93.
The Parameterized Approximability of TSP with Deadlines, Hans-Joachim Böckenhauer, Juraj Hromkovič, Joachim Kneis, Joachim Kupke, Theory of Computing Systems, vol. 41/3 (2007), pp. 431-444.
Descriptional and Computational Complexity in Relation to the Practicability of Computation and Computational Modes, Joachim Kupke, 2006.
On Separating Constant from Polynomial Ambiguity of Finite Automata, Joachim Kupke, Proc. of the 32nd International Conference on Current Trends in Theory and Practice of Computer Science (SOFSEM '06), LNCS 3831, 2006, pp. 379-388.
On the Approximation Hardness of Some Generalizations of TSP, Hans-Joachim Böckenhauer, Juraj Hromkovič, Joachim Kneis, Joachim Kupke, SWAT, 2006, pp. 184-195.
Reusing Optimal TSP Solutions for Locally Modified Input Instances, Hans-Joachim Böckenhauer, Luca Forlizzi, Juraj Hromkovič, Joachim Kneis, Joachim Kupke, Guido Proietti, Peter Widmayer, Proc. of the 4th IFIP International Conference on Theoretical Computer Science (IFIP TCS 2006).