This morning, I came across a post on the APA Style Blog* on citing works from the spirit world. Just in time for Halloween!
From the 2013 blog post:
Noncorporeal beings have dictated a number of bestsellers, yet they never seem to cash their own royalty checks. For bibliographic purposes, the author is the person through whom the work entered the corporeal realm.
So, such a citation would be:
Medium Last Name, Medium First Name. (Year). Title of publication. Location: Publisher.
There are also entire subject headings on Spirit Writings (a search of which [search su:Spirt writings. in our catalog] will bring up all sorts of resources from UMass and the Five Colleges!
*APA is the format I know best, so I am biased towards it!
Hume-Pratuch, J. (2013, October 31). APA Style Blog: How to Cite Works From the Spirit World. Retrieved October 30, 2014, from http://blog.apastyle.org/apastyle/2013/10/how-to-cite-works-from-the-spirit-world.html