ε Freud, Sigmund. "Three Essays on the Theory of Sexuality" The Standard Edition of the Complete Psychological Works of Sigmund Freud vol. 7. London: Vintage Books, 2001. p. 213
ε Freud, Sigmund. "Three Essays on the Theory of Sexuality" The Standard Edition of the Complete Psychological Works of Sigmund Freud vol. 7. London: Vintage Books, 2001. p. 213