Adaptive Leader-Following Consensus for Uncertain Euler-Lagrange Systems   under Directed Switching Networks
  The leader-following consensus problem for multiple Euler-Lagrange systems was studied recently by the adaptive distributed observer approach under the assumptions that the leader system is neurally stable and the communication network is jointly connected and undirected. In this paper, we will study the same problem without assuming that the leader system is neutrally stable, and the communication network is undirected. The effectiveness of this new result will be illustrated by an example. 
Tao Liu and Jie Huang
math.OC