Institution: | Department of Analysis, Eötvös Loránd University, Budapest, Pázmány Péter sétány 1/C, 1117 Hungary -- and -- Department of Mathematics, University College London, Gower Street, London, WC1E 6BT, England ; Department of Mathematics, Imperial College, Huxley Building, 180 Queen's Gate, London, SW7 2AZ, England |