อ้างอิง ของ แคปต์ชา

  1. ↑ "The reCAPTCHA Project – Carnegie Mellon University CyLab". www.cylab.cmu.edu. สืบค้นเมื่อ 2017-01-13.
  2. ↑ von Ahn, Luis; Blum, Manuel; Hopper, Nicholas J.; Langford, John (May 2003). CAPTCHA: Using Hard AI Problems for Security. EUROCRYPT 2003: International Conference on the Theory and Applications of Cryptographic Techniques.
  3. ↑ "Method and system for discriminating a human action from a computerized action". 2004-03-01. Cite journal requires |journal= (help)