Communications of the ACM November 2000 Ultra-high-density Data Storage p 65 Phase Change Recording by Henk van Houten and Wouter Leibbrandt CD: 650 MB, lambda = 780 nm, Numerical Aperture = 0.45 DVD: 4.7 GB, lambda = 650 nm, NA = 0.6 DVR: 22 GB, lambda = 400 nm, NA = 0.85 p 89 Seven Comments on Charging and Billing by Philip Ginzboorg