Levitt, E. E. (1967). The psychology of anxiety (ed.). Bobbs-Merrill.
Lua i Stíl Chicago (17ú heag.)Levitt, Eugene E. The Psychology of Anxiety. ed. Indianapolis: Bobbs-Merrill, 1967.
Lua MLA (9ú heag.)Levitt, Eugene E. The Psychology of Anxiety. ed. Bobbs-Merrill, 1967.
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