George Caspar Homans (1910-1989) in the book Human Group published in 1950: We mean by a group a number of persons who communicate with one another often over a span of time, and who are few enough so that each person is able to communicate with all others, not at secondhand, through other people, but face-to-face.

Prezentacja PowerPoint:
i_84_0_Anatomy_of_Groups.ppt