Iranian Mathematical Society (IMS) Bulletin of the Iranian Mathematical Society 1017-060X 37 No. 3 2011 09 15 Symmetric curvature tensor249 267 en A. Heydari N. Boroojerdian E. Peyghan 2009 08 22 Curvature tensor Derivation Fr"{o}licher-Nijenhuis bracket Lie derivative symmetric differential symmetric curvature