1. Stephen Ellis, ‘Nature and origin of virtual environments: a bibliographic essay’, Computing Systems in Engineering, 2(4), page 325
2. The Dream Machine—Exploring the Computer Age;Palfreman,1991
3. The ultimate display;Sutherland;Proceedings of International Federation of Information Processing Congress,1965
4. A head-mounted three dimensional display;Sutherland,1968
5. Virtual Reality;Rheingold,1991