1. Balaguer JF (1993) Virtual Studio. PhD Thesis, EPFL, Switzerland.
2. Balaguer JF, Gobbetti E (1995) Animating Spaceland. IEEE Computer28 (7).
3. Balaguer JF, Gobbetti E (1995) Sketching 3D Animations. Proc. EUROGRAPHICS: 241–258.
4. Blake E, Hoole Q (1992) Expressing Relationships between Objects: Problems and Solutions. Proc. Third EUROGRAPHICS Workshop on Object-Oriented Graphics: 159–162.
5. Borning A, Freeman-Benson B, Wilson M (1992) Constraint Hierarchies. Lisp and Symbolic Computation5 (3): 221–268.