1. Zhang J. Approximating the two-level facility location problem via a quasi-greedy approach. In: Proceedings of the 15th ACM-SIAM Symposium on Discrete Algorithms. 2004, 801–810
2. Sun D, Hao Z. Group nearest neighbor queries based on voronoi diagrams. Application Research of Computers, 2010, 47(7): 1244–1251
3. Hao Z, Liu Y. Reverse nearest neighbor search in spatial database. Computer Science, 2005, 32(11): 115–118
4. Farahani R, Asgari N, Heidari N, Hosseininia M, Goh M. Covering problems in facility location: a review. Computers & Industrial Engineering, 2012, 62(1): 368–407
5. Xia T, Zhang D, Kanoulas E, Du Y. On computing top-t most influential spatial sites. In: Proceedings of the International Conference on Very Large Data Bases. 2005, 946–957