S. Izumiya, COMPLETELY INTEGRABLE HOLONOMIC SYSTEMS OF FIRST-ORDER DIFFERENTIAL-EQUATIONS, Proceedings of the Royal Society of Edinburgh. Section A. Mathematics, 125, 1995, pp. 567-586
We classify completely integrable holonomic systems of first-order dif
ferential equations for one real-valued function by equivalence under
the group of point transformations in the sense of Sophus Lie. In orde
r to pursue the classification, we use the notion of one parameter Leg
endrian unfoldings which induces a special class of divergent diagrams
of map germs which are called integral diagrams. Our normal forms are
represented by integral diagrams.