1. E. Blucher, private communication.
2. Electro-weak radiative corrections for e+e− → μ+μ− at LEP energies
3. M. Consoli, W. Hollik, F. Jegerlehner, in Z physics at LEP 1, CERN Yellow Report 89-08, eds. G. Altarelli, R. Kleiss and C. Verzegnassi, Vol. 1, p. 7, and references therein