Não informado. (1976). Essence. York University, Atkinson College, Department of Psychology.
Chicago-referens (17:e uppl.)Não informado. Essence. Ontario, Canada: York University, Atkinson College, Department of Psychology, 1976.
MLA-referens (8:e uppl.)Não informado. Essence. York University, Atkinson College, Department of Psychology, 1976.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.