Here is one more link on the subject (I couldn't get the one above to work for me)
http://www.eftuniverse.com/
This is a site with a vested interest (they have products they are selling) So you will have to do your research on it.
I am not personally endorsing the site in any way, as I do not know enough about it to have an opinion one way or the other about it.
However, it does look like it has a lot of information on this technique that you could at least read up on.
S.C.