中国科学院数学与系统科学研究院期刊网
The Backup 2-Median Problem on Block Graphs
Yu-kun CHENG, Li-ying KANG, Hong YAN
Acta Mathematicae Applicatae Sinica(English Series) . 2014, (2): 309 -320 .  DOI: 10.1007/s10255-014-0294-y