@ARTICLE{yue2020directed,  
	author={D. {Yue} and S. {Baldi} and J. {Cao} and Q. {Li} and B. {De Schutter}},  
	journal={IEEE Transactions on Control of Network Systems},   
	title={A Directed Spanning Tree Adaptive Control Solution to Time-Varying Formations},   
	year={2021},
	volume={8},
	number={2},
	pages={690-701}, 
	doi={10.1109/TCNS.2021.3050332}
}