Böckenhauer, Hans-Joachim, Luca Forlizzi, Juraj Hromkovic, Joachim Kneis, Joachim Kupke, Guido Proietti, and Peter Widmayer. 2007. “On the Approximability of TSP on Local Modifications of Optimally Solved Instances”. Algorithmic Operations Research 2 (2), 83. https://journals.lib.unb.ca/index.php/AOR/article/view/2803.