BULLETIN OF THE AUSTRALIAN MATHEMATICAL SOCIETY, vol.64, no.2, pp.201-212, 2001 (SCI-Expanded)
Chen (1999) established a sharp relationship between the Ricci curvature and the squared mean curvature for a submanifold in a Riemanian space form with arbitrary codimension. Matsumoto (to appear) dealt with similar problems for submanifolds in complex space forms.