Naoki Hayashi Toshimitsu Ushio Performance Consensus Problem of Multi-Agent Systems with Multiple State Variables. 2403-2410 2008 91-A IEICE Transactions 9 http://dx.doi.org/10.1093/ietfec/e91-a.9.2403 db/journals/ieicet/ieicet91a.html#HayashiU08