@article {5366,
	title = {Space-time crystals of trapped ions},
	year = {2012},
	doi = {10.1103/PhysRevLett.109.163001},
	author = {Tongcang Li and Zhe-Xuan Gong and Zhang-Qi Yin and H.T. Quan and Xiaobo Yin and Peng Zhang and L.-M. Duan and Xiang Zhang}
}
