1. Ingemar Bengtsson, Wojciech Bruzda, Asa Ericsson, Jan-Ake Larsson, Wojciech Tadej, and Karol Zyczkowski, Mutually unbiased bases and Hadamard matrices of order six, J. Math. Phys. 48 (2007), no. 052106, 1–21.[doi/arXiv]