1. see e. g.G. Altarelli, Phys. Rep. 81 (19S2) 1
2. L. Maiani, lectures in this volume
3. F. Berends, lectures in this volume
4. V. Khoze, lecture in this volume
5. T. Sjöstrand et al., ‘QCD Generators for LEP’, in eds.G. Altarelli, R. Kleiss, C. Verzegnassi, CERN 89-08, volume 3, p. 143