S. Narayanan, M. Kaimal, K. Bijlani, M. Prasanth, and K. Kumar. Proceedings of the 2014 International Conference on Interdisciplinary Advances in Applied Computing, page 51:1--51:5. New York, NY, USA, ACM, (2014)
M. Mavrikis, and S. Gutierrez-Santos. Computers & Education, 54 (3):
641 - 651(2010)Learning in Digital Worlds: Selected Contributions from the CAL 09 Conference.