1. School of Mathematical Sciences, Queen Mary University of London, London E1 4NS, UK.
2. Departament d’Enginyeria Informatica i Matematiques, Universitat Rovira i Virgili, 43007 Tarragona, Spain.
3. Instituto de Física Interdisciplinar y Sistemas Complejos IFISC (CSIC-UIB), Campus UIB, 07122 Palma de Mallorca, Spain.
4. Integrated Science Lab, Department of Physics, Umeå University, SE-901 87 Umeå, Sweden.
5. RTE Réseau de Transport d’Electricité, Paris, France.