Iranian Mathematical Society (IMS) Bulletin of the Iranian Mathematical Society 1017-060X 38 2 2011 02 23 Recurrent metrics in the geometry of second order differential equations391 401 en Mircea Crasmareanu Faculty of Mathematics University "Al. I. Cuza" Iasi, 700506 2011 02 09 Semispray nonlinear connection recurrent metric Obata operators