“…Email: longwang@pku.edu.cn is equivalent to that of a pair of submatrices of Laplacian matrix. In what follows, some related results on the controllability of continuous-time systems are proposed, such as first-order and high-order multi-agent systems in Wang, Jiang, Xie, and Ji (2009), switching topology and time delay in Ji, Wang, Lin, and Wang (2010), equitable and relaxed equitable partition in Rahmani, Ji, Mesbahi, and Egerstedt (2009) and external equitable partition in O'Clery, Yuan, Stan, and Barahona (2013). For the controllability of discrete-time systems, the controllability conditions for first-order multi-agent systems with switching topology are proposed in Liu, Chu, Wang, and Xie (2008).…”