TITLE: Quasi-periodic response solutions at normal-internal resonances AUTHORS: Henk Broer^(1), Heinz Hanssmann^(2), Angel Jorba^(3), Jordi Villanueva^(4), Florian Wagener^(5) (1) broer@math.rug.nl Instituut voor Wiskunde en Informatica (IWI), Rijksuniversiteit Groningen, Postbus 800, 9700 AV Groningen, The Netherlands. (2) Heinz@iram.rwth-aachen.de Institut fur Reine und Angewandte Mathematik der RWTH Aachen, 52056 Aachen, Germany. (3) angel@maia.ub.es Departament de Matematica Aplicada i Analisi, Universitat de Barcelona, Gran Via 585, 08007 Barcelona, Spain. (4) jordi@vilma.upc.es Departament de Matematica Aplicada I, Universitat Politecnica de Catalunya, Diagonal 647, 08028 Barcelona, Spain. (5) f.o.o.wagener@uva.nl Center for Nonlinear Dynamics in Economics and Finance (CeNDEF), Department of Quantitative Economics, Universiteit van Amsterdam, Roetersstraat 11, 1018 WB Amsterdam, The Netherlands. ABSTRACT: In the conservative dynamics of certain quasi-periodically forced oscillators, normal-internal resonances are considered in a bifurcational setting. The unforced system is a one degree of freedom oscillator, under forcing the system becomes a skew-product flow with a quasi-periodic motion on an $n$-dimensional torus as driving system. In this work, we investigate the persistence and the bifurcations of quasi-periodic $n$-dimensional tori (so-called ``resonse solutions'') in the averaged system, filling normal-internal resonance `gaps' that had been excluded in previous analyses. This is a summary of a talk at the Equadiff meeting held in Hasselt, Belgium, July 22-26, 2003.