Zhigeng Pan Adrian David Cheok Hongwei Yang Jiejie Zhu Jiaoying Shi Virtual Reality and Mixed Reality for Virtual Learning Environments. 6 2006 conf/edutainment/2006 Edutainment http://dx.doi.org/10.1007/11736639_4 db/conf/edutainment/edutainment2006.html#PanCYZS06