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Dream interpretation is the process of assigning meaning to dreams. In many ancient societies, such as those of Egypt and Greece, dreaming was considered a supernatural communication or a means of divine intervention, whose message could be unravelled by people with certain powers.
In modern times, various schools of psychology and neurobiology have offered theories about the meaning and purpose of dreams. Most people currently appear to interpret dream content according to the Freudian theory of dreams in countries, as found by a study conducted in the United States, India, and South Korea.
People appear to believe dreams are particularly meaningful: they assign more meaning to dreams than to similar waking thoughts. For example, people report they would be more likely to cancel a trip they had planned that involved a plane flight if they dreamt of their plane crashing the night before than if they thought of their plane crashing the night before or the Department of Homeland Security issued a Federal warning.
However, people do not attribute equal importance to all dreams. People appear to use motivated reasoning when interpreting their dreams. They are more likely to view dreams confirming their waking beliefs and desires to be more meaningful than dreams that contradict their waking beliefs and desires.
One of the earliest written examples of dream interpretation comes from the Babylonian Epic of Gilgamesh. Gilgamesh dreamt that an axe fell from the sky. The people gathered around it in admiration and worship. Gilgamesh threw the axe in front of his mother and then he embraced it like a wife. His mother, Ninsun, interpreted the dream. She said that someone powerful would soon appear. Gilgamesh would struggle with him and try to overpower him, but he would not succeed. Eventually they would become close friends and accomplish great things. She added, "That you embraced him like a wife means he will never forsake you. Thus your dream is solved." While this example shows the tendency to see dreams as mantic (as predicting the future), Ninsun's interpretation anticipates a contemporary approach. The axe, phallic and aggressive, symbolizes a male who will start as aggressive but turn into a friend. To embrace an axe is to transform aggression into affection and camaraderie. Later, a compendium of dream omens, the "Dream Book" or Iškar Zaqīqu was assembled.
In ancient Egypt, priests acted as dream interpreters. Hieroglyphics depicting dreams and their interpretations are evident. Dreams have been held in considerable importance through history by most cultures.
The ancient Greeks constructed temples they called Asclepieions, where sick people were sent to be cured. It was believed that cures would be effected through divine grace by incubating dreams within the confines of the temple. Dreams were also considered prophetic or omens of particular significance. Artemidorus of Daldis, who lived in the 2nd century AD, wrote a comprehensive text Oneirocritica (The Interpretation of Dreams). Although Artemidorus believed that dreams can predict the future, he presaged many contemporary approaches to dreams. He thought that the meaning of a dream image could involve puns and could be understood by decoding the image into its component words. For example, Alexander, while waging war against the Tyrians, dreamt that a satyr was dancing on his shield. Artemidorus reports that this dream was interpreted as follows: satyr = sa tyros ("Tyre will be thine"), predicting that Alexander would be triumphant. Freud acknowledged this example of Artemidorus when he proposed that dreams be interpreted like a rebus.
In medieval Islamic psychology, certain hadiths indicate that dreams consist of three parts, and early Muslim scholars recognized three kinds of dreams: false, patho-genetic, and true. Ibn Sirin (654–728) was renowned for his Ta'bir al-Ru'ya and Muntakhab al-Kalam fi Tabir al-Ahlam, a book on dreams. The work is divided into 25 sections on dream interpretation, from the etiquette of interpreting dreams to the interpretation of reciting certain Surahs of the Qur'an in one's dream. He writes that it is important for a layperson to seek assistance from an alim (Muslim scholar) who could guide in the interpretation of dreams with a proper understanding of the cultural context and other such causes and interpretations. Al-Kindi (Alkindus) (801–873) also wrote a treatise on dream interpretation: On Sleep and Dreams. In consciousness studies, Al-Farabi (872–951) wrote the On the Cause of Dreams, which appeared as chapter 24 of his Book of Opinions of the people of the Ideal City. It was a treatise on dreams, in which he was the first to distinguish between dream interpretation and the nature and causes of dreams. In The Canon of Medicine, Avicenna extended the theory of temperaments to encompass "emotional aspects, mental capacity, moral attitudes, self-awareness, movements and dreams." Ibn Khaldun's Muqaddimah (1377) states that "confused dreams" are "pictures of the imagination that are stored inside by perception and to which the ability to think is applied, after (man) has retired from sense perception."
A standard traditional Chinese book on dream-interpretation is the Lofty Principles of Dream Interpretation (夢占逸旨) compiled in the 16th century by Chen Shiyuan (particularly the "Inner Chapters" of that opus). Chinese thinkers also raised profound ideas about dream interpretation, such as the question of how we know we are dreaming and how we know we are awake. It is written in the Chuang-tzu: "Once Chuang Chou dreamed that he was a butterfly. He fluttered about happily, quite pleased with the state that he was in, and knew nothing about Chuang Chou. Presently he awoke and found that he was very much Chuang Chou again. Now, did Chou dream that he was a butterfly or was the butterfly now dreaming that he was Chou?" This raises the question of reality monitoring in dreams, a topic of intense interest in modern cognitive neuroscience.
In the 17th century the English physician and writer Sir Thomas Browne wrote a short tract upon the interpretation of dreams. Dream interpretation was taken up as part of psychoanalysis at the end of the 19th century; the perceived, manifest content of a dream is analyzed to reveal its latent meaning to the psyche of the dreamer. One of the seminal works on the subject is The Interpretation of Dreams by Sigmund Freud.
A paper in 2009 by Carey Morewedge and Michael Norton in the Journal of Personality and Social Psychology found that most people believe that "their dreams reveal meaningful hidden truths." In one study conducted in the United States, South Korea and India, they found that 74% of Indians, 65% of South Koreans and 56% of Americans believed their dream content provided them with meaningful insight into their unconscious beliefs and desires. This Freudian view of dreaming was endorsed significantly more than theories of dreaming than attribute dream content to memory consolidation, problem solving, or random brain activity. This belief appears to lead people to attribute more importance to dream content than to similar thought content that occurs while they are awake. In one study in the paper, Americans were more likely to report that they would miss their flight if they dreamt of their plane crashing than if they thought of their plane crashing the night before flying (while awake), and that they would be as likely to miss their flight if they dreamt of their plane crashing the night before their flight as if there was an actual plane crash on the route they intended to take. Not all dream content was considered equally important. Participants in their studies were more likely to perceive dreams to be meaningful when the content of dreams was in accordance with their beliefs and desires while awake. People were more likely to view a positive dream about a friend to be meaningful than a positive dream about someone they disliked, for example, and were more likely to view a negative dream about a person they disliked as meaningful than a negative dream about a person they liked.
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It was in his book The Interpretation of Dreams (Die Traumdeutung; literally "dream-interpretation"), first published in 1899 (but dated 1900), that Sigmund Freud first argued that the motivation of all dream content is wish-fulfillment, and that the instigation of a dream is often to be found in the events of the day preceding the dream, which he called the "day residue." In the case of very young children, Freud claimed, this can be easily seen, as small children dream quite straightforwardly of the fulfillment of wishes that were aroused in them the previous day (the "dream day"). In adults, however, the situation is more complicated—since in Freud's submission, the dreams of adults have been subjected to distortion, with the dream's so-called "manifest content" being a heavily disguised derivative of the "latent" dream-thoughts present in the unconscious. As a result of this distortion and disguise, the dream's real significance is concealed: dreamers are no more capable of recognizing the actual meaning of their dreams than hysterics are able to understand the connection and significance of their neurotic symptoms.
In Freud's original formulation the latent dream-thought was described as having been subject to an intra-psychic force referred to as "the censor"; in the more refined terminology of his later years, however, discussion was in terms of the super-ego and "the work of the ego's forces of defense." In waking life, he asserted, these so-called "resistances" altogether prevented the repressed wishes of the unconscious from entering consciousness; and though these wishes were to some extent able to emerge during the lowered state of sleep, the resistances were still strong enough to produce "a veil of disguise" sufficient to hide their true nature. Freud's view was that dreams are compromises which ensure that sleep is not interrupted: as "a disguised fulfilment of repressed wishes," they succeed in representing wishes as fulfilled which might otherwise disturb and waken the dreamer.
Freud's "classic" early dream analysis is that of "Irma's injection": in that dream, a former patient of Freud's complains of pains. The dream portrays Freud's colleague giving Irma an unsterile injection. Freud provides us with pages of associations to the elements in his dream, using it to demonstrate his technique of decoding the latent dream thought from the manifest content of the dream.
Freud described the actual technique of psychoanalytic dream-analysis in the following terms, suggesting that the true meaning of a dream must be "weeded out" from dream:
You entirely disregard the apparent connections between the elements in the manifest dream and collect the ideas that occur to you in connection with each separate element of the dream by free association according to the psychoanalytic rule of procedure. From this material you arrive at the latent dream-thoughts, just as you arrived at the patient's hidden complexes from his associations to his symptoms and memories... The true meaning of the dream, which has now replaced the manifest content, is always clearly intelligible. [Freud, Five Lectures on Psycho-Analysis (1909); Lecture Three]
Freud listed the distorting operations that he claimed were applied to repressed wishes in forming the dream as recollected: it is because of these distortions (the so-called "dream-work") that the manifest content of the dream differs so greatly from the latent dream thought reached through analysis—and it is by reversing these distortions that the latent content is approached.
The operations included:
- Condensation – one dream object stands for several associations and ideas; thus "dreams are brief, meagre and laconic in comparison with the range and wealth of the dream-thoughts."
- Displacement – a dream object's emotional significance is separated from its real object or content and attached to an entirely different one that does not raise the censor's suspicions.
- Visualization – a thought is translated to visual images.
- Symbolism – a symbol replaces an action, person, or idea.
To these might be added "secondary elaboration"—the outcome of the dreamer's natural tendency to make some sort of "sense" or "story" out of the various elements of the manifest content as recollected. (Freud, in fact, was wont to stress that it was not merely futile but actually misleading to attempt to "explain" one part of the manifest content with reference to another part as if the manifest dream somehow constituted some unified or coherent conception).
Freud considered that the experience of anxiety dreams and nightmares was the result of failures in the dream-work: rather than contradicting the "wish-fulfillment" theory, such phenomena demonstrated how the ego reacted to the awareness of repressed wishes that were too powerful and insufficiently disguised. Traumatic dreams (where the dream merely repeats the traumatic experience) were eventually admitted as exceptions to the theory.
Freud famously described psychoanalytic dream-interpretation as "the royal road to a knowledge of the unconscious activities of the mind"; he was, however, capable of expressing regret and dissatisfaction at the way his ideas on the subject were misrepresented or simply not understood:
|“||The assertion that all dreams require a sexual interpretation, against which critics rage so incessantly, occurs nowhere in my Interpretation of Dreams ... and is in obvious contradiction to other views expressed in it.||”|
On another occasion, he suggested that the individual capable of recognizing the distinction between latent and manifest content "will probably have gone further in understanding dreams than most readers of my Interpretation of Dreams".
Although not dismissing Freud's model of dream interpretation wholesale, Carl Jung believed Freud's notion of dreams as representations of unfulfilled wishes to be limited. Jung argued that Freud's procedure of collecting associations to a dream would bring insights into the dreamer's mental complex—a person's associations to anything will reveal the mental complexes, as Jung had shown experimentally—but not necessarily closer to the meaning of the dream. Jung was convinced that the scope of dream interpretation was larger, reflecting the richness and complexity of the entire unconscious, both personal and collective. Jung believed the psyche to be a self-regulating organism in which conscious attitudes were likely to be compensated for unconsciously (within the dream) by their opposites.
Jung proposed two basic approaches to analyzing dream material: the objective and the subjective. In the objective approach, every person in the dream refers to the person they are: mother is mother, girlfriend is girlfriend, etc. In the subjective approach, every person in the dream represents an aspect of the dreamer. Jung argued that the subjective approach is much more difficult for the dreamer to accept, but that in most good dream-work, the dreamer will come to recognize that the dream characters can represent an unacknowledged aspect of the dreamer. Thus, if the dreamer is being chased by a crazed killer, the dreamer may come eventually to recognize his own homicidal impulses. Gestalt therapists extended the subjective approach, claiming that even the inanimate objects in a dream can represent aspects of the dreamer.
Jung believed that archetypes such as the animus, the anima, the shadow and others manifested themselves in dreams, as dream symbols or figures. Such figures could take the form of an old man, a young maiden or a giant spider as the case may be. Each represents an unconscious attitude that is largely hidden to the conscious mind. Although an integral part of the dreamer's psyche, these manifestations were largely autonomous and were perceived by the dreamer to be external personages. Acquaintance with the archetypes as manifested by these symbols serve to increase one's awareness of unconscious attitudes, integrating seemingly disparate parts of the psyche and contributing to the process of holistic self-understanding he considered paramount.
Jung believed that material repressed by the conscious mind, postulated by Freud to comprise the unconscious, was similar to his own concept of the shadow, which in itself is only a small part of the unconscious.
Jung cautioned against blindly ascribing meaning to dream symbols without a clear understanding of the client's personal situation. He described two approaches to dream symbols: the causal approach and the final approach. In the causal approach, the symbol is reduced to certain fundamental tendencies. Thus, a sword may symbolize a penis, as may a snake. In the final approach, the dream interpreter asks, "Why this symbol and not another?" Thus, a sword representing a penis is hard, sharp, inanimate, and destructive. A snake representing a penis is alive, dangerous, perhaps poisonous and slimy. The final approach will tell additional things about the dreamer's attitudes.
Technically, Jung recommended stripping the dream of its details and presenting the gist of the dream to the dreamer. This was an adaptation of a procedure described by Wilhelm Stekel, who recommended thinking of the dream as a newspaper article and writing a headline for it. Harry Stack Sullivan also described a similar process of "dream distillation."
Although Jung acknowledged the universality of archetypal symbols, he contrasted this with the concept of a sign—images having a one to one connotation with their meaning. His approach was to recognize the dynamism and fluidity that existed between symbols and their ascribed meaning. Symbols must be explored for their personal significance to the patient, instead of having the dream conform to some predetermined idea. This prevents dream analysis from devolving into a theoretical and dogmatic exercise that is far removed from the patient's own psychological state. In the service of this idea, he stressed the importance of "sticking to the image"—exploring in depth a client's association with a particular image. This may be contrasted with Freud's free associating which he believed was a deviation from the salience of the image. He describes for example the image "deal table." One would expect the dreamer to have some associations with this image, and the professed lack of any perceived significance or familiarity whatsoever should make one suspicious. Jung would ask a patient to imagine the image as vividly as possible and to explain it to him as if he had no idea as to what a "deal table" was. Jung stressed the importance of context in dream analysis.
Jung stressed that the dream was not merely a devious puzzle invented by the unconscious to be deciphered, so that the true causal factors behind it may be elicited. Dreams were not to serve as lie detectors, with which to reveal the insincerity behind conscious thought processes. Dreams, like the unconscious, had their own language. As representations of the unconscious, dream images have their own primacy and mechanics.
Jung believed that dreams may contain ineluctable truths, philosophical pronouncements, illusions, wild fantasies, memories, plans, irrational experiences and even telepathic visions. Just as the psyche has a diurnal side which we experience as conscious life, it has an unconscious nocturnal side which we apprehend as dreamlike fantasy. Jung would argue that just as we do not doubt the importance of our conscious experience, then we ought not to second guess the value of our unconscious lives.
In 1953, Calvin S. Hall developed a theory of dreams in which dreaming is considered to be a cognitive process. Hall argued that a dream was simply a thought or sequence of thoughts that occurred during sleep, and that dream images are visual representations of personal conceptions. For example, if one dreams of being attacked by friends, this may be a manifestation of fear of friendship; a more complicated example, which requires a cultural metaphor, is that a cat within a dream symbolizes a need to use one's intuition. For English speakers, it may suggest that the dreamer must recognize that there is "more than one way to skin a cat," or in other words, more than one way to do something.
Faraday, Clift, et al.
In the 1970s, Ann Faraday and others helped bring dream interpretation into the mainstream by publishing books on do-it-yourself dream interpretation and forming groups to share and analyze dreams. Faraday focused on the application of dreams to situations occurring in one's life. For instance, some dreams are warnings of something about to happen—e.g. a dream of failing an examination, if one is a student, may be a literal warning of unpreparedness. Outside of such context, it could relate to failing some other kind of test. Or it could even have a "punny" nature, e.g. that one has failed to examine some aspect of his life adequately.
Faraday noted that "one finding has emerged pretty firmly from modern research, namely that the majority of dreams seem in some way to reflect things that have preoccupied our minds during the previous day or two."
In the 1980s and 1990s, Wallace Clift and Jean Dalby Clift further explored the relationship between images produced in dreams and the dreamer's waking life. Their books identified patterns in dreaming, and ways of analyzing dreams to explore life changes, with particular emphasis on moving toward healing and wholeness.
Primitive instinct rehearsal theory of dreaming
Two researchers have postulated that dreams have a biological function, where the content requires no analysis or interpretation, that content providing an automatic stimulation of the body's physiological functions underpinning the human instinctive behavior. So dreams are part of the human, and animal, survival and development strategy. - Professor Antti Revonsuo (2000) has limited his ideas to those of "threat rehearsal," where dreams exercise our primary self-defense instincts, and he has argued this cogently in a number of publications.
Keith Stevens extends the theory to all human instincts, including threats to self, threats to family members, pair bonding and reproduction, inquisitiveness and challenges, and the drive for personal superiority and tribal status. He categorizes dreams, using a sample of 22,000 Internet submissions, into nine categories, demonstrating the universal commonality of dream content and instinct rehearsal. It is postulated that the dream function is automatic, in response to the content, exercising and stimulating the body chemistry and neurological activity that would come into play if the scenario occurred in real life, so that the dream does not have to be remembered to achieve its objective.
It is argued that, once a dreamer has experienced a threat in a dream (either to self or a family member), his/her ability to confront and overcome a real life threat is then enhanced, so that such dreams, in both humans or animals, are an aid to survival. The threat rehearsal can be specific, for instance, an attack from a savage dog, but it can also be general, in that the threat response physiology is activated and reinforced whilst dreaming.
For human reproduction, the theory states that dreams of pairing, bonding and mating stimulate the reflex to reproduce the species, with an emphasis on dreams that promote the principle of selection; the desire of the individual to find the best mate and to achieve the optimum genetic mixing. In that respect, the dream function conflicts with human values of fidelity and mating for life. Specifically, young women dream often of being pregnant and giving birth, overwhelmingly positive dreams that directly stimulate the urge to reproduce.
Regarding status, dreams about being superior or inferior to others are thought to stimulate the dreamer's determination to improve his status within the immediate human hierarchy, either through the positive physiology of success or the negative physiology of failure. Hence, dreaming is believed to promote competition and the reproductive success of those best suited to the environment.
Finally, other dreams stimulate the determination to explore and inquire, through the extremes of exhilarating dream achievements (positive physiology) or frustrating obstructions and barriers. The latter stimulates a determination not to give up in a quest, so that, in life, the individual and the species move forward. For the dreaming wildebeest, it may be a rich pasture over the hill; for the human dreamer it may be splitting the atom.
- Dream dictionary
- Dream journal
- Dream sharing
- Psychoanalytic dream interpretation
- Recurring dream
- Morewedge, Carey K.; Norton, Michael I. "When dreaming is believing: The (motivated) interpretation of dreams.". Journal of Personality and Social Psychology. 96 (2): 249–264. doi:10.1037/a0013264.
- Thompson, R. (1930) The Epic of Gilgamesh. Oxford: Oxford University Press.
- George, A. trans. (2003) The Babylonian Gilgamesh Epic: Critical Edition and Cuneiform Texts. Oxford, UK: Oxford University Press.
- Oppenheim, A. (1956) The interpretation of dreams in the ancient Near East with a translation of an Assyrian dreambook. Transactions of the American Philosophical Society, 46(3): 179–373. p. 247.
- Artemidorus (1990) The Interpretation of Dreams: Oneirocritica. White, R., trans., Torrance, CA: Original Books, 2nd Edition.
- Freud, S. (1900) The Interpretation of Dreams. New York: Avon, 1980.
- (Haque 2004, p. 376)
- (Haque 2004, p. 375)
- (Haque 2004, p. 361)
- (Haque 2004, p. 363)
- Lutz, Peter L. (2002), The Rise of Experimental Biology: An Illustrated History, Humana Press, p. 60, ISBN 0-89603-835-1
- Ibn Khaldun, Franz Rosenthal, N.J. Dawood (1967), The Muqaddimah, trans., p. 338, Princeton University Press, ISBN 0-691-01754-9
- Lofty Principles of Dream Interpretation, "Inner Chapters 1–4"
- Lofty Principles of Dream Interpretation, "Inner Chapter 5"
- Lofty Principles of Dream Interpretation, "Inner Chapters 6–9"
- Lofty Principles of Dream Interpretation, "Inner Chapter 10"
- Johnson, M.; Kahan, T.; Raye, C. (1984). "Dreams and reality monitoring". Journal of Experimental Psychology: General. 113: 329–344. doi:10.1037/0096-3418.104.22.1689.
- Blechner, M (2005). "Elusive illusions: Reality judgment and reality assignment in dreams and waking life". Neuro-Psychoanalysis. 7: 95–101. doi:10.1080/15294145.2005.10773477.
- Matalon, Nadav (2011). "The Riddle Of Dreams". Philosophical Psychology. 24 (4): 517–536. doi:10.1080/09515089.2011.556605.
- Wilson, Cynthia (3 April 2012). "Remembering and Understanding your Dreams". Womenio. Retrieved 28 May 2012.
- Gray, R. (9 January 2012). "Lecture Notes: Freud's Conception of the Psyche (Unconscious) and His Theory of Dreams". University of Washington. Retrieved 28 May 2012.
- Freud, S. (1900) op.cit., (1919 edition), p. 397
- Jung, C.G. (1902) The associations of normal subjects. In: Collected Works of C. G. Jung, vol. 2. Princeton, NJ: Princeton University Press, pp. 3–99.
- Jacobi, J. (1973) The Psychology of C. G. Jung. New Haven, CT: Yale University Press.
- Storr, Anthony (1983). The Essential Jung. New York. ISBN 0-691-02455-3.
- Jung, C.G. (1948) General aspects of dream psychology. In: Dreams. trans., R. Hull. Princeton, NJ: Princeton University Press, 1974, pp. 23–66.
- Jung, C.G. (1948) op.cit.
- Stekel, W. (1911) Die Sprache des Traumes (The Language of the Dream). Wiesbaden: J.F. Berman
- Sullivan, H.S. (1953) The Interpersonal Theory of Psychiatry. New York: Norton.
- Jung, Carl (1934). The Practice of Psychotherapy. The Practical Use of Dream-analysis. p. 147. ISBN 0-7100-1645-X.
- Calvin S. Hall. "A Cognitive Theory of Dreams". dreamresearch.net. Retrieved 7 October 2010.
- Faraday, Ann. The Dream Game. p. 3.
- Clift, Jean Dalby; Clift, Wallace (1984). Symbols of Transformation in Dreams. The Crossroad Publishing Company. ISBN 0-8245-0653-7.; Clift, Jean Dalby; Clift, Wallace (1988). The Hero Journey in Dreams. The Crossroad Publishing Company. ISBN 0-8245-0889-0.; Clift, Jean Dalby (1992). Core Images of the Self: A Symbolic Approach to Healing and Wholeness. The Crossroad Publishing Company. ISBN 0-8245-1218-9.
- Aziz, Robert (1990). C.G. Jung's Psychology of Religion and Synchronicity (10 ed.). The State University of New York Press. ISBN 0-7914-0166-9.
- Aziz, Robert (1999). "Synchronicity and the Transformation of the Ethical in Jungian Psychology". In Becker, Carl. Asian and Jungian Views of Ethics. Greenwood. ISBN 0-313-30452-1.
- Aziz, Robert (2007). The Syndetic Paradigm: The Untrodden Path Beyond Freud and Jung. The State University of New York Press. ISBN 978-0-7914-6982-8.
- Aziz, Robert (2008). "Foreword". In Storm, Lance. Synchronicity: Multiple Perspectives on Meaningful Coincidence. Pari Publishing. ISBN 978-88-95604-02-2.
- Doniger O'Flaherty, Wendy (1986). Dreams, Illusion, and Other Realities. University of Chicago Press. ISBN 0-226-61855-2.
- Freud, Sigmund (1966). Introductory Lectures. W.W. Norton. p. 334.
- Freud, Sigmund (1900). The Interpretation of Dreams. Macmillan.
- Freud, Sigmund (1920). A General Introduction to Psychoanalysis. Boni & Liveright.
- Hall, James (1983). Jungian Dream Interpretation: A Handbook of Theory and Practice. Inner City Books. ISBN 0-919123-12-0.
- Sechrist, Elsie with foreword by Cayce, Hugh Lynn (1974). Dreams, Your Magic Mirror. Warner Books. ISBN 0-446-31384-X.