2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/48973The conventional NLO parton model is enough for the description of total cross sections and one-particle distributions. In the case of two-particle correlations, the collinear approximation has failed, and it is necessary to account for the transverse momenta of initial partons. The different possibilities to do this are discussed.10 pages, LaTeX, 6 figures, epsfig.sty. Talk, given at HERA Monte Carlo Workshop, 27-30 April 1998, DESY, HamburgHigh Energy Physics - Phenomenologytext