by M. Marvan
Differential Geometry and Applications, Proc. Conf. Brno, 1995 (Masaryk University, Brno, 1996) 393–402
Recursion operators are operators taking symmetries to symmetries. In this paper we identify recursion operators with Backlund auto- transformations of the "linearization" of the diffiety. This class of recursion operators is closed with respect to the composition and the inversion, and includes recent generalization by Guthrie when the number of independent variables is two. In multidimension there are no nontrivial operators in Guthrie's sense unless for very overdetermined equations.