1. See, for instance, G. Sterman, in: D.E. Soper (Ed.), QCD and beyond, Proceedings of the Theoretical Advanced Study Institute TASI'95, World Scientific, Singapore, 1996, p.327.
2. Transverse momentum distribution in Drell-Yan pair and W and Z boson production
3. For recent studies in this direction, see C. Friberg, T. Sjöstrand, hep-ph/9906316; S. Mrenna, hep-ph/9902471.
4. J.C. Collins, in: A.H. Mueller (Ed.), Perturbative Quantum Chromodynamics, World Scientific, Singapore, 1989, p.573.
5. F.V. Tkachov, Int. J. Mod. Phys. A 8 (1993) 2047; F.V. Tkachov, hep-ph/9703423.