“…The main ingredients in our proof are almost conservation law for the solution to the KdV equation in spaces of analytic functions and spacetime dyadic bilinear estimates associated with the KdV equation. For similar studies for the Dirac-Klein-Gordon system, generalized KdV and cubic NLS see [32,16,31,34]. For studies on related issues for nonlinear partial differential equations see for instance [5,6,7,9,14,17,8,15,18,28,19,29,26].…”