Calibration of centre-of-mass energies at LEP1 for precise measurements of Z properties by Assmann, R, Boge, M, Billen, R, Blondel, A, Bravin, E, Bright-Thomas, P, Camporesi, T, Dehning, B, Drees, A, Duckeck, G, Gascon, J, Geitz, M, Goddard, B, Hawkes, C, Henrichsen, K, Hildreth, MD, Hofmann, A, Jacobsen, R, Koratzinos, M, Lamont, M, Lancon, E, Lucotte, A, Mnich, J, Mugnai, G, Peschardt, E