«Zener Cards». Glossary of Skepticism & the Paranormal. About.com. Arxivat de l'original el 2012-02-18. [Consulta: 20 desembre 2006].
worldcat.org
Terence., Hines,. Pseudoscience and the paranormal (en anglès). 2a ed. Amherst, N.Y.: Prometheus Books, 2003, p. 122. ISBN 1573929794. «The procedural errors in the Rhine experiments have been extremely damaging to his claims to have demonstrated the existence of ESP. Equally damaging has been the fact that the results have not replicated when the experiments have been conducted in other laboratories»