Ooops, I just noticed that Jane Lyzell, former sidekick of trumpet-swinging British fraud Colin Fry, claims that the facts are already there for you to find, if you just bother to check. But she is not willing to back up her claim with links, since this generation lives in "syberspayce" (I think it means "cyberspace"). The right thing to do, according to Lyzell, is to search for knowledge in our libraries and ask psychics. Then you will discover the real facts! Indeed, Helen Duncan was tested! (And was declared an obvious fraud, but I think Lyzell missed that shelf.) Anyway, in an act of benevolence, Lyzell suggests an old title from 1922 by Björke. I happen to have it and it's the standard anecdotal stories being repeated over and over again on the internet, with the exception of a few Scandinavian cases. But since she is devoted to books, there are some titles I would like to suggest for her to read:
"A Beginners Guide to the Swedish Language"
"Hair-care for Dummies"
"Sociopathy and hysteria combined? How to adapt to social contexts."
I'm sure Lyzell will find them if she just bothers to check...