It is considered responsible conduct of research to always use primary sources. Sometimes, however, this is not possible due to practical reasons. When the original source is referred to in another text and one still wishes to refer to the original source, we talk about using a so-called secondary source. It must always be made clear to the reader if secondary sources are used. The secondary source is written in square brackets. Both the primary and the secondary source must be listed in the list of references.
Lewin’s [1951; 1958] well-known change management model consists of three stages (Hitt, Miller & Colella 2009, 493).
The change process of an organization can be divided into three stages (Hitt, Miller & Colella 2009, 493 [Lewin 1951; Lewin 1958]).
In the list of references secondary sources are listed in the same way as primary sources:
Hitt, M.A., Miller, C.C. & Colella A. 2009. Organizational Behavior: A Strategic Approach, 2nd Edition. Jefferson City: John Wiley & Sons, Inc.
Lewin, K. 1951. Field theory in social science. New York: Harper & Row.
Lewin, K. 1958. Group decisions and social change. In E.E. Maccobby, T.M. Newcomb & E.L. Hartley (eds.) Readings in social psychology, 3rd Edition. Austin, TX: Holt, Rinehart & Winston, 201 – 216.