1. De generali quadam aequatione differentiali tertii ordini;Kummer;Progr. Evang. Königl. Stadtgymnasium Liegnitz,1834
2. Invariants, covariants and quotient-derivatives associated with linear differential equations;Forsyth;Philos. Trans. R. Soc. Lond. Ser. A,1899
3. Projective Differential Geometry of Curves and Ruled Surfaces;Wilczynski,1906
4. Über transformationen von differentialgleichungen;Stäckel,1897
5. Theorie der Transformationgruppe;Lie,1930