Full context:   Tuckman reviewed a collection of fifty published articles concerned with group development over a period of time in order to classify the types of study they related to, group purpose and a hypothesized series of stages. The articles referred to studies of groups working together within a variety of therapeutic and professional settings, and to groups with inter-personal development as their purpose and groups with other task purposes. It was his analysis of these fifty articles which led Tuckman to formulate his four-stage model.