1. For the author list of the OPAL collaboration refer to G. Abbiendi et al., Eur. Phys. J. C 71, 1733 (2011). arXiv:1101.1470 [hep-ex]
2. MCnet Collaboration, A. Buckley et al., Phys. Rep. 504, 145 (2011). arXiv:1101.2599 [hep-ph]
3. J. Beringer et al. Particle Data Group, Phys. Rev. D 86, 010001 (2012)
4. M. H. Seymour and M. Marx, arXiv:1304.6677 [hep-ph]
5. S. Gieseke, Prog. Part. Nucl. Phys. 72, 155 (2013)