I find it comical that some of those who deny psychic activity use psychic explanations to deny the findings.
There have been several who have claimed that what appears to be mediumship could be explained by telepathy.
Um... I thought you people didn't believe in psychic ability? How can you use one type of ability to deny another, when you don't believe in either? I don't consider that a scientific approach.
The Society for Scientific Exploration has been putting a lot of its older issues online, free to everyone. Here's a particularly good article on the subject.
If you can't get that directly, start here and click on 'Communicating with the dead', then on the full-text link. It's a PDF file so you'll need the Adobe Acrobat reader.