R.W. Lindeman, J.L. Sibert, and J.K. Hahn.
Towards Usable VR: An Empirical Study of User Interfaces for
Immersive Virtual Environments.
In Proceedings of CHI 99. Institute for Computer Graphics,
George Washington University, Washington, DC, 1999.
(pdf)
(bibtex:
Lindeman-1999-TUV).