[1]
A. Archer, M. H. Bateni, M. T. Hajiaghayi, and H. Karloff, Improved approximation algorithms for prize-collecting Steiner tree and TSP, SIAM J. Compt. vol. 40, no. 2, pp. 309–332, 2011.
[2]
D. Bienstock, M. X. Goemans, D. Simchi-Levi, and D. P. Williamson, A note on the prize collecting traveling salesman problem, Mathematical Programming, vol. 59, nos. 1–3, pp. 413–420, 1993.
[3]
F. A. Chudak, T. Roughgarden, and D. P. Williamson, Approximate k-MSTs and k-Steiner trees via the primal-dual method and Lagrangean relaxation, Mathematical Programming, vol. 100, no. 2, pp. 411–421, 2004.
[4]
L. Han, D. Xu, D. Du, and C. Wu, A 5-approximation algorithm for the k-prize-collecting Steiner tree problem, Optimization Letters, vol. 13, no. 3, pp. 573–585, 2019.
[5]
L. Han, D. Xu, D. Du, and C. Wu, A primal-dual algorithm for the generalized prize-collecting Steiner forest problem, Journal of the Operations Research Society of China, vol. 5, no. 2, pp. 219–231, 2017.
[6]
L. Han, D. Xu, D. Du, and D. Zhang, An approximation algorithm for the uniform capacitated k-means problem, Journal of Combinatorial Optimization, .
[7]
L. Han, D. Xu, D. Du, and D. Zhang, A local search approximation algorithm for the uniform capacitated k-facility location problem, Journal of Combinatorial Optimization, vol. 35, no. 2, pp. 409–423, 2018.
[8]
L. Han, D. Xu, M. Li, and D. Zhang, Approximation algorithms for the robust facility leasing problem, Optimization Letters, vol. 12, no.3, pp. 625–637, 2018.
[9]
L. Han, D. Xu, Y. Xu, and D. Zhang, Approximating the τ-relaxed soft capacitated facility location problem, Journal of Combinatorial Optimization, vol. 40, no.3, pp. 848–860, 2020.
[10]
J. Li, A. M. V. V. Sai, X. Cheng, W. Cheng, Z. Tian, and Y. Li, Sampling-based approximate skyline query in sensor equipped IoT networks, Tsinghua Science and Technology, vol. 26, no. 2, pp. 219–229, 2021.
[11]
R. Ravi, R. Sundaram, M. V. Marathe, D. J. Rosenkrantz, and S. S. Ravi, Spanning trees short or small, SIAM J. Discrete Math., vol. 9, no. 2, pp. 178–200, 1996.
[12]
Y. Xu, R. H. Möhring, D. Xu, Y. Zhang, and Y. Zou, A constant FPT approximation algorithm for hard-capacitated k-means, Optimization and Engineering, vol. 21, no. 3, pp. 709–722, 2020.
[13]
Y. Xu, D. Xu, D. Du, and C. Wu, Improved approximation algorithm for universal facility location problem with linear penalties, Theoretical Computer Science, vol. 774, pp. 143–151, 2019.
[14]
Y. Xu, D. Xu, D. Du, and C. Wu, Local search algorithm for universal facility location problem with linear penalties, Journal of Global Optimization, vol 67, nos. 1&2, pp. 367–378, 2017.
[15]
Y. Xu, D. Xu, D. Du, and D. Zhang, Approximation algorithm for squared metric facility location problem with nonuniform capacities, Discrete Applied Mathematics, vol. 264, pp. 208–217, 2019.
[16]
Y. Xu, D. Xu, Y. Zhang, and J. Zou, MpUFLP: Universal facility location problem in the p-th power of metric space, Theoretical Computer Science, vol. 838, pp. 58–67, 2020.
[17]
Y. Zhang and H. Zhu, Approximation algorithm for weighted weak vertex cover, Journal of Computer Science and Technology, vol. 19, no. 6, pp. 782–786, 2004.
[18]
M. X. Goemans and D. P. Williamson, A general approximation technique for constrained forest problems, SIAM J. Comput., vol. 24, no. 2, pp. 296–317, 1995.
[19]
S. Arora and G. Karakostas, A 2 + ε approximation algorithm for the k-MST problem, in Proc. of the 11th Annual ACM-SIAM Symposium on Discrete Algorithms, San Francisco, CA, USA, 2000, pp. 754–759.
[20]
S. Arya and H. A. Ramesh, A 2.5-factor approximation algorithm for the k-MST problem, Information Processing Letters, vol. 65, no. 3, pp. 117–118, 1998.
[21]
B. Awerbuch, Y. Azar, A. Blum, and S. Vempala, New approximation guarantees for minimum-weight k-trees and prize-collecting salesmen, SIAM J. Comput., vol. 28, no. 1, pp. 254–262, 1999.
[22]
A. Blum, R. Ravi, and S. Vempala, A constant-factor approximation algorithm for the k-MST problem, in Proc. of the 28th Annual ACM Symposium on Theory of Computing, Philadelphia, PA, USA, 1996, pp. 442–448.
[23]
M. Fischetti, H. W. Hamacher, K. Jørnsten, and F. Maffioli, Weighted k-cardinality trees: Complexity and polyhedral structure, Networks, vol. 24, no. 1, pp. 11–21, 1994.
[24]
N. Garg, A 3-approximation for the minimum tree spanning k vertices, in Proc. of the 37th Annual Symposium on Foundations of Computer Science, Burlington, VT, USA, 1996, pp. 302–309.
[25]
N. Garg, Saving an epsilon: A 2-approximation for the k-MST problem in graphs, in Proc. of the 37th Annual ACM Symposium on Theory of Computing, Baltimore, MD, USA, 2005, pp. 396–402.
[26]
Y. Matsuda and S. Takahashi, A 4-approximation algorithm for k-prize collecting Steiner tree problems, Optimization Letters, vol. 13, no. 2, pp. 341–348, 2019.