1. Jones, L.M. (1982), “Defining system boundaries in practice: some proposals and guidelines”, Journal of Applied Systems Analysis, Vol. 9, pp. 41‐55.
2. Langefors, B. (1995), Essays on Infology, Studentlitteratur, Lund.
3. von Bertalanffy, L. (1968), General Systems Theory Foundations, Development, Applications, Revised edition, George Braziller, New York, NY.