F. Steinicke, G. Bruder, and K. Hinrichs. Symposium on Virtual Reality and Software Technology (VRST) (Poster Presentation), page 229--230. ACM, ACM Press, (2007)
H. Xiong, P. Curzon, S. Tahar, and A. Blandford. Integrated Formal Methods, 2335, Springer Berlin, Heidelberg, The original publication is available at www.springerlink.com.(2002)