P. Sander, J. Snyder, S. Gortler, and H. Hoppe. SIGGRAPH '01: Proceedings of the 28th annual conference on Computer graphics and interactive techniques, page 409--416. New York, NY, USA, ACM, (2001)
R. Yang, D. Gotz, J. Hensley, H. Towles, and M. Brown. VIS '01: Proceedings of the conference on Visualization '01, page 167--174. Washington, DC, USA, IEEE Computer Society, (2001)