1. Department of Biochemical Engineering, University College London, Bernard Katz Building, London WC1E 6BT, U.K.
2. Department of Mathematics, University College London, Gower Street, London WC1E 6BT, U.K.
3. Institute for Women's Health, University College London, London WC1E 6AU, U.K.
4. School of Medicine, Medical Sciences and Nutrition, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, U.K.
5. Department of Physics, Institute for Complex Systems and Mathematical Biology, Meston Building, Old Aberdeen, Aberdeen, U.K.
6. Oscillation Theory Department, Lobachevsky State University of Nizhniy Novgorod, Novgorod, Russia
7. Department of Control Theory and Systems Dynamics, Lobachevsky State University of Nizhniy Novgorod, Novgorod, Russia