中国科学院数学与系统科学研究院期刊网
AMS
On Well-posed Mutually Nearest and Mutually Furthest Point Problems in Banach Spaces
Chong LI, Ren Xing NI
Acta Mathematica Sinica . 2004, (1): 147 -156 .  DOI: 10.1007/s10114-003-0287-x