1[1]Al Gore. The digitl Earth: Understanding our planet in the 21st century. At the Califomia Science Center,Los Angels,California , on January 31,1998.
5[5]M Reddy, Y G Leclerc, et al. Modeling the Digital Earth in VRML[R]. ALC technical Report No.559, SRI international, Menlo,park CA, 9. November, 1998.