1. Geometrical Methods in the Theory of Ordinary Differential Equations;Arnold,1988
2. Algebraic definition of central dispersion of the 1st kind of the differential equation;Barvinek;Czech. Math. J.,1966
3. Linear Differential Transformation of the Second Order;Boruvka,1971
4. Les Problemes d'equivalence, Seminaire de Mathematiques, expose du 1 mars 1937;Cartan,1955
5. Les Problemes d'equivalence, Seminaire de Mathematiques, expose du 1 mars 1937;Cartan,1955