1. Department of Mathematics and Statistics and Neuroscience Institute, Georgia State University, 30 Pryor Street, Atlanta, Georgia 30303, USA
2. Department of Control Theory, Lobachevsky State University of Nizhny Novgorod, 23, Gagarin Ave., Nizhny Novgorod 603950, Russia
3. Department of Mathematics, Volga State University of Water Transport, 5A, Nesterov Str., Nizhny Novgorod 603950, Russia