Sigmund Freud, manuscript postcard of May 18, 1905, to Paul Federn (Private collection) | Portrait photograph (ca. 1938) | Gesammelte Werke, Bd. XIII, Jenseits des Lustprinzips, London, 1940; and Studien zur Psychoanalyse der Neurosen, Leipzig, Vienna, 1926 (Both books, private collection)