One study, by psychologist Imants Barušs, was unable to replicate suggested paranormal origins for EVP recorded under controlled conditions.[36] Brian Regal in Pseudoscience: A Critical Encyclopedia (2009) has written "A case can be made for the idea that many EVPs are artifacts of the recording process itself with which the operators are unfamiliar. The majority of EVPS have alternative, nonspiritual sources; anomalous ones have no clear proof they are of spiritual origin."[37]