On completeness of the Ribaucour transformations for triply orthogonal   curvilinear coordinate systems in R^3
  In this paper we solve positively the problem of (local) density of solutions of the (2+1)-dimentional integrable system describing triply orthogonal curvilinear coordinates in R^3 (a (2+1)-dimensional generalization of the 3-wave system) obtainable from a given initial solution with consecutive B\"acklund transformations (called Ribaucour transformations in classical differential geometry) in the space of all solutions of the system in question. 
E. I. Ganzha (Krasnoyarsk State Pedagogical University)