CAPTCHA Suitable for Smartphones. - Yusuke Tsuruta; Mayumi Takaya; Akihiro Yamamura (ICT-EurAsia, 2013)

Reverse Turing Test using Touchscreens and CAPTCHA. - Mayumi Takaya; Yusuke Tsuruta; Akihiro Yamamura (J. Wirel. Mob. Networks Ubiquitous Comput. Dependable Appl., 2013)