@techreport{FujiiKimKojimaetal.2023, author = {Koichi Fujii and Sunyoung Kim and Masakazu Kojima and Hans D. Mittelmann and Yuji Shinano}, title = {An Exceptionally Difficult Binary Quadratic Optimization Problem with Symmetry: a Challenge for The Largest Unsolved QAP Instance Tai256c}, institution = {ZIB}, address = {Takustr. 7, 14195 Berlin}, number = {23-27}, language = {eng}, year = {2023} }