Bruce Greyson is a researcher in the field of near-death studies and has been called the father of research in near-death experiences. Greyson, along with Kenneth Ring, Michael Sabom, and others, built on the research of Raymond Moody, Jr, Russell Noyes and Elisabeth Kübler-Ross. Greyson's scale to measure the aspects of near-death experiences has been widely used, being cited 95 times as of early 2010. He also devised a 19-item scale to assess experience of kundalini, the Physio-Kundalini Scale.
Book: The Handbook of Near-Death Experiences: Thrity Years of Investigation