The rational generalized integrating factors for first-order ODEs
  We describe a solving semi-decision method based on examination of the rational structures of the generalized integrating factors of first-order ODEs. We propose a conjecture that for some family of equations of the type dy/dx=P(x,y)/Q(x,y), with P and Q polynomials only in y (or in x), the general form of the structures of generalized integrating factors are rational in y (or in x). In such a way one can obtain a differential-algebraic polynomial system for undetermined parameters of the structures. The successful solution of this system (it is sufficient to find any particular solution) automatically leads to finding the general solutions of ODEs. 
Yu.N. Kosovtsov