Conformally symmetric manifolds and quasi conformally recurrent Riemannian manifolds

In order to give a new proof of a theorem concerned with conformally symmetric Riemannian manifolds due to Roter and Derdzinsky [8], [9] and Miyazawa [15], we have adopted the technique used in a theorem about conformally recurrent manifolds with harmonic conformal curvature tensor in [3]. In this paper, we also present a new proof of a successive refined version of a theorem about conformally recurrent manifolds with harmonic conformal curvature tensor. Moreover, as an extension of theorems mentioned above we prove some theorems related to quasi conformally recurrent Riemannian manifolds with harmonic quasi conformal curvature tensor.