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(6) Rudolph, Heinrich. Der Ausdruck der Gemütsbewegungen des Menschen dargestellt und erklärt auf Grund der Urformen-und der Gesetze des Ausdrucks und der Erregungen. Dresden, 1903.

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(8) Cannon, Walter B. Bodily Changes in Pain, Hunger, Fear, and Rage. An account of recent researches into the function of emotional excitement. New York and London, 1915.

(9) Hirn, Yrjö. The Origins of Art. A psychological and sociological, inquiry. London and New York, 1900.

(10) Bergson, H. Le Rire. Essai sur la signification du comique. Paris, 1900.

(11) Sully, James. An Essay on Laughter. Its forms, its causes, its development, and its value. London and New York, 1902.

(12) Dugas, L. Psychologie du rire. Paris, 1902.

(13) Groos, Karl. The Play of Man. Translated from the German by Elizabeth L. Baldwin. New York, 1901.

(14) ——. The Play of Animals. Translated from the German by Elizabeth L. Baldwin. New York, 1898.