中国科学院数学与系统科学研究院期刊网
The Isometric Extension of the Into Mapping from the Unit Sphere S1(E) to S1(l(Γ)
Xiao Hong FU
Acta Mathematica Sinica . 2008, (9): 1475 -1482 .  DOI: 10.1007/s10114-008-7286-x