BULLETIN OF THE KOREAN MATHEMATICAL SOCIETY, cilt.54, sa.1, ss.253-264, 2017 (SCI-Expanded)
We first extend Yano-Nomizu's theorem, which characterizes extrinsic spheres in a Riemannian manifold, for Riemannian maps. Then we introduce Clairaut Riemannian maps, give an example and obtain necessary and sufficient conditions for a Riemannian map to be Clairaut type.