"Group Psychology and the Analysis of the Ego" Sigmund Freud (1921), in the Standard Edition of the Complete Psychological Works of Sigmund Freud; edited by James Strachey, Vol. XVIII. The Hogarth Press, London, 1955.
2.
"Group Psychotherapy, A Review of Recent Literature", Giles W. Thomas; in Psychosomatic Medicine , Vol. II., April 1943.
3.
"Some Theoretical Aspects of Group Psychotherapy" Nathan W. Ackerman; in Group Psychotherapy: A Symposium, edited by J.C. Moreno, Beacon House, New York , 1946.
4.
"The Application of Group Concepts to the Treatment of the Individual in the Group" S.H. Foulkes (1958). Paper presented at the New York Academy of Medicine, September 1958, and published at Postgraduate Center for Psychotherapy, 218 East 70 Street, New York, 21, New York.
