1. Solutions in the general solution;Cohn,1977
2. Differential Algebra and Algebraic Groups;Kolchin,1973
3. Jacobi's bound for the order of systems of first order differential equations;Lando;Trans. Amer. Math. Soc.,1970
4. Extensions of differential places;Morrison;Amer. J. Math.,1978
5. Differential Algebra;Ritt,1950