D. Jung, and S. Jones. Proceedings of the 22nd Conference of the Computer-Human Interaction Special Interest Group of Australia on Computer-Human Interaction, page 33--40. New York, NY, USA, ACM, (2010)
S. Shang, B. Yuan, K. Deng, K. Xie, and X. Zhou. Proceedings of the 19th ACM SIGSPATIAL International Conference on Advances in Geographic Information Systems, page 181--190. New York, NY, USA, ACM, (2011)