Shelley Adler (15 de enero de 2011). Sleep Paralysis: Night-mares, Nocebos, and the Mind-Body Connection. Rutgers University Press. pp. 3-. ISBN978-0-8135-5237-8. Consultado el 10 de febrero de 2013. «In the field of sleep research, this experience is termed sleep paralysis: an individual, in the process of falling asleep or awakening, finds himself or herself completely awake, but unable to move or speak…Frequently, he or she sees a shadowy or indistinct shape approaching and becomes increasingly terrified.».
Clare Oakley; Amit Malik (15 de noviembre de 2011). Rapid Psychiatry. John Wiley & Sons. pp. 6-. ISBN978-1-118-29418-5. Consultado el 10 de febrero de 2013.