This article will be available on 01/Feb/2011

Z, Ji, Z, Wang, H, Lin and Z, Wang, Controllability of multi-agent systems with time-delay in state and switching topology, International Journal of Control, Volume 83, Issue 2 February 2010 , pages 371 - 386, (ISSN 0020-7179). Taylor and Francis. http://dx.doi.org/10.1080/00207170903171330