中国科学院数学与系统科学研究院期刊网
The Pinching Theorems about Sectional Curvature of Submanifolds on Unit Sphere
Ding Xing DING,Hong An SUN,Qin
Acta Mathematica Sinica, Chinese Series . 2003, (1): 37 -48 .  DOI: 10.12386/A2003sxxb0007