Managing Dynamic User Communities in a Grid of Autonomous Resources Yazar: Alfieri, R, Cecchini, R, Ciaschini, V, dell'Agnello, L, Gianoli, A, Spataro, F, Bonnassieux, F, Broadfoot, P, Lowe, G, Cornwall, L, Jensen, J, Kelsey, D, Frohner, Á, Groep, D, de Cerff, W, Steenbakkers, M, Venekamp, G, Kouril, D, McNab, A, Mulmo, O, Silander, M, Hahkala, J, Lörentey, K