Valery Tereshko^1,* and Elena Shchekinova^2,†

• ¹Communications Research Laboratory, McMaster University, 1280 Main Street West, Hamilton, Ontario Canada L8S 4K1 and The Nonlinear Centre, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge CB3 9EW, United Kingdom
• ²Center for Dynamical Systems and Nonlinear Studies, School of Mathematics, Georgia Institute of Technology, Atlanta, Georgia 30332

• ^*Author to whom correspondence should be addressed. Present address: The Nonlinear Centre, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge CB3 9EW, U.K. Electronic address: V.Tereshko@damtp.cam.ac.uk
• ^†Electronic address: elenash@math.gatech.edu