Hiroshi Ito Pierdomenico Pepe Zhong-Ping Jiang A small-gain condition for integral input-to-state stability of interconnected retarded nonlinear systems. 19-24 2008 CDC http://dx.doi.org/10.1109/CDC.2008.4739018 conf/cdc/2008 db/conf/cdc/cdc2008.html#ItoPJ08