Progress in FWSD non-linear effects with XRLs S.J. Topping, R. Keenan, C.L.S. Lewis, R.M.N. O’Rourke, A.G. MacPhee, S. Dobosz, G.J. Tallents, M. Notely and D. Neely J. Phys. IV France, 11 PR2 (2001) Pr2-487-Pr2-490 DOI: 10.1051/jp4:2001293