Lehdonvirta, V., Soma, H., Ito, H., Yamabe, T., Kimura, H., & Nakajima, T. (2009) UbiPay: Minimizing Transaction Costs with Smart Mobile Payments.Proceedings of the 6th International Conference on Mobile Technology, Application & Systems (Mobility 2009), Nice, France, September 2-4. New York: ACM. (demonstration video)