Visual word-based CAPTCHA using 3D characters. - Cristina Romero Macias; Ebroul Izquierdo (ICDP, 2009)

Image CAPTCHA based on distorted faces. - Cristina Romero Macias; Ebroul Izquierdo (ICDP, 2011)

Image understanding for automatic human and machine separation. - Cristina Romero Macias (2013)