1. Ackoff, R.L., “Towards a Systems of Systems Concepts”, Management Science, 17, 11 (1971), 661–671.
2. Alter, S., Information Systems: A Management Perspective, The Benjamin/Cummings Publishing Company, 1996.
3. Amaral, L.A.M.d., PRAXIS: Um referencial para o Planeamento de Sistemas de Informaçâo, Tese de Doutoramento, Universidade do Minho, 1994 (in Portuguese).
4. Avison, D.E. and G. Fitzgerald, Information Systems Development: Methodologies, Techniques and Tools, Blackwell, 1988.
5. Avison, D.E. and A.T. Wood-Harper, “Multiview–An Exploration in Information Systems Development”, The Australian Computer Journal, 18, 4 (1986), 174–179.