Problems

Ackoff, Russell L. and Fred E. Emery
[1972]  On Purposeful Systems, Tavistock Publications, London

Broadbent, Geoffrey and Anthony Ward editors
[1969]  Design Methods in Architecture, Architectural Association Paper nº 14, Lund Humphries, London

Chadwick, George
[1971]  A Systems View of Planning, Pergamon Press, Oxford

Dunker, Karl
[1945]  On problem-solving, in Wason, P. C. and Johnson-Laird, editors [1968]  Thinking and Reasoning, Penguin, Harmondsworth

Hoc, Jean-Michel
[1987, French Edition]  Cognitive Psychology of Planning, Academic Press, London, 1988
French Title : Psychologie Cognitive de la Planification

Mayer, Richard E.
[1983]  Thinking, Problem Solving, Cognition, W. H. Freeman & Co., New York, Second Edition 1992

Merton, Robert K.
[1959]  Notes on Problem-Finding in Sociology, in Sociology Today, edited with Leonard Broom and Leonard S. Cottrell, jr., Harper & Row, New York, 1965