References
[Grötschel et al., 1993]
Grötschel, Martin; Lovász, László, and Schrijver, Alexander. Geometric algorithms and combinatorial optimization. Second corrected edition. Berlin: Springer; 1993. ISBN: 3-540-56740-2.
Cyberspace geography visualization - 15 October 1995
Luc Girardin, The Graduate Institute of International Studies