2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/39369xloops is a program package that calculates Feynman diagrams by using computer algebra systems. In this paper it is shown which problems to be solved by computer algebra arise during such calculations, and how this problems are handled in the framework of xloops.Contribution to Proceedings of 6th Rhine Workshop on Computer Algebra (Sankt Augustin, Germany, March-April 1998), ed. J. CalmetHigh Energy Physics - Phenomenologytext