1Chi Chung Ko, Chen B M, Shaoyan Hu, et al. A web-based vir- tual laboratory on a frequency modulation experimen[J]. IEEE Transactions on Systems, Man and Cybernetics, 2001,31 (3) : 295-303.
2Latta J N, Oberg D J. A conceptual virtual reality model[J]. IEEE CGN-A,2002(8) .-23-29.
