1. ARIES Conceptstation, Aries Technology Inc. Lowell, MA
2. SDRCI-DEAS VI, Structural Dynamics Research Corporation, 200 Eastman Drive, Milford, Ohio 45150-2789
3. Intergraph, Intergraph Corporation, Huntsville, Alabama 35894-001
4. PRO/Engineer, Parametric Technology Corporation, 128 Technology Drive, Waltham, MA 02154
5. Schielen, W. (Editor) (1989) Multibody Systems Handbook, Springer-Verlag, New York