1. Alexander, F.: Fundamentals of Psycho-analysis. New York: W. W. Norton & Co., Inc., 1948, 188 and 190.
2. Alexander, F.: A Contribution to the Theory of Play. Reprinted from the Psychoanalytic Quarterly, Vol. XXVII: 175–193, 1958.
3. Alexander, F.: loc. cit. 191.
4. Alexander, F.: loc. cit. 192.
5. Erikson, E. H.: Studies in the Interpretation of Play, 1. Clinical Observation of Play Disruption in Young Children, Genetic Psychological Monographs, XXII, 1940, 563–564.