@inproceedings{bui2008necessary,
title={Necessary conditions for multiobjective optimal control problems with free end-time},
author={Bui Trong Kien, Ngai-Ching Wong, and J-C Yao},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191020210505114166211},
booktitle={SIAM Journal on Control and Optimization},
volume={47},
number={5},
pages={2251-2274},
year={2008},
}
Bui Trong Kien, Ngai-Ching Wong, and J-C Yao. Necessary conditions for multiobjective optimal control problems with free end-time. 2008. Vol. 47. In SIAM Journal on Control and Optimization. pp.2251-2274. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191020210505114166211.