1. Wolf, T., Brand, A. (1992): The computer algebra package CRACK for investi-gating PDEs. Manual for the package CRACK in the Reduce network library and in Pommaret, J. (ed.): Proceedings of ERCIM School on Partial Differential Equations and Group Theory, April 1992 in Bonn ,pp. 1–19. GMD, Bonn
2. Hereman, W. (1995): Symbolic software for Lie symmetry analysis. In Ibrag-imov, N.N. (ed.): CRC Handbook of Lie Group Analysis of Differential Equa-tions, Vol. 3: New Trends in Theoretical Developments and Computational Methods ,pp. 367–413. CRC Press, Boca Raton, Florida
3. Wolf, T., Brand, A. (1995): Examples of the investigation of differential equa-tions with modularized programs. To be published in Mathematical and Com-puter Modelling
4. Riquier, C. (1910): Les systemes d’equations aux derivees partielles. Gauthier-Villars, Paris
5. Thomas, J. (1937): Differential systems. AMS Colloquium publications 21, American Mathematical Society, New York