1. School of Electrical Engineering (EES), KTH Royal Institute of Technology, 100 44 Stockholm, Sweden
2. Aerospace Engineering and Institute for Systems Research, University of Maryland, College Park, Maryland 20742
3. Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109
4. Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104
5. Control and Dynamical Systems, California Institute of Technology, Pasadena, California 91125