@conference {MMB-CDC08, title = {Controllability Decompositions of Networked Systems Through Quotient Graphs}, booktitle = {Proc. IEEE Int. Conf. on Decision and Control}, year = {2008}, pages = {5244 - 5249}, keywords = {Embedded Control, Robotics}, author = {S. Martini and M. Egerstedt and A. Bicchi} }