Rui Xu; Pingyuan Cui; Dong Qiao & Enjie Luan (March 18, 2007). "Design and optimization of trajectory to Near-Earth asteroid for sample return mission using gravity assists". Advances in Space Research. 40 (2): 200–225. Bibcode:2007AdSpR..40..220X. doi:10.1016/j.asr.2007.03.025.
Rui Xu; Pingyuan Cui; Dong Qiao & Enjie Luan (March 18, 2007). "Design and optimization of trajectory to Near-Earth asteroid for sample return mission using gravity assists". Advances in Space Research. 40 (2): 200–225. Bibcode:2007AdSpR..40..220X. doi:10.1016/j.asr.2007.03.025.