Constructing Secure Audio CAPTCHAs by Exploiting Differences between Humans and Machines. - Hendrik Meutzner; Santosh Gupta; Dorothea Kolossa (CHI, 2015)

Toward Improved Audio CAPTCHAs Based on Auditory Perception and Language Understanding. - Hendrik Meutzner; Santosh Gupta; Viet-Hung Nguyen; Thorsten Holz; Dorothea Kolossa (ACM Trans. Priv. Secur., 2017)